How I Met Your Mother

Season 6

Big Days

1. Ted and Lily share a nervous/subconscious tick of peeling off/ripping up labels off bottles (water or beer). Lily does it when she feels guilty (Season 3 Episode 7 Dowisetrepla) while Ted does it when he's nervous (Season 6 Episode 1 Big Days).
2. Barney's comment "Are you there, Barney? It's me, horny" references Judy Blume's book Are You There God? It's Me, Margaret.
3. About 11 minutes in, One of Marshall's coworkers yells "spank that butt big fudge" while he is walking down the hall to go home and impregnate Lily. Big Fudge is the nickname Marshall uses at the bar as skee ball champion in Jenkins (season 5 episode 13). It is revealed in season 10 that he earned the nickname through eating a block of fudge to celebrate getting into law school.
4. Barney's description of Robin having squiggly lines drawn all over her and her appearance refers to Peanuts character Pig-Pen.
5. The church at the beginning of the episode is the same church in the show 7th heaven.
6. In real life the actress playing 'the hot girl at the bar' named her second child "Sebastian Danger Fitzpatrick". They may have given the child that middle name so he could later say "Danger? I laugh in the face of danger! Danger is my middle name!! ". This will be literally true because his middle name is Danger and people will most certainly laugh in his face.
7. Cindy's date is reading Brideshead Revisited by Evelyn Waugh at the bar.

Cleaning House

1. Barney's bedroom has the exact same layout as Eric Forman's from that 70's show.
2. In a deleted scene from this episode, as the gang talk about lies their parents told them, Ted reveals that his mom told him he was allergic to bacon. It then goes into a flashback from when Ted accidentally ate bacon in college and thought he was going to die. Since this scene was cut, they re-did this storyline in season 9 when Ted eats a lifetime's worth of bacon to make up for all he missed out on.
3. In this episode, Robin mentions Robert De Niro in Cape Fear. In the film, Robert De Niro's character has a tattoo on his chest that says "Loretta". Incidentally, Barney's mother's name is also Loretta.
4. In this episode Barney's bedroom is shown to have a regular wooden bedframe whereas in the Season 4 Episode 15 'The Stinsons' he says he has a racecar bed.
5. Ben Vereen, who plays James' father 'Sam' plays the father of Will in Fresh Prince of Bel-Air (1990). In both scenarios, he plays a man with a complicated relationship with his son.
6. In his childhood room, Barney has either a Macintosh Classic (originally released in 1990) or a Macintosh Classic II (originally released in 1992).

Unfinished

1. Ted and Marshall discuss at length the fatal flaw of the Death Star in Star Wars, in that a single blast fired into a particular vent would reach the reactor core and cause the entire ship to explode and be destroyed. Specifically, they debate whether it was the fault of the "architect" who designed it, or the "contractor" who built it. It has now been explained (retconned in a sense) in Rogue One: A Star Wars Story (2016) that this was neither a design flaw nor a construction error, but was a deliberate act of sabotage by the "architect" (actually scientist/engineer) who designed it, Galen Erso, with the intent of providing a method for the rebels to destroy it.
2. Marshall and Lily make several comments about what a good couple Ted and Barney would be. Neil Patrick Harris and Josh Radnor played a couple in the play "The Paris Letter".
3. When Robin deletes Don's phone number officially, the camera shows a close-up shot of her phone. On her phone shows a list of her contacts after Don's number is removed. One of the contacts is named David Baker. David Baker is the property master for the show.
4. At the beginning of 'Unfinished', you hear Franz Schubert's Symphony No.8 which is popularly known as Unfinished Symphony which he composed in 1822 but left unfinished.
5. Marshall makes a reference about Ted's building being like the Death Star from Star Wars. In the next scene Ted is wearing a long sleeve white shirt with a black vest. This is a clear reference to Han Solo from Star Wars
6. In addition to the show's property manager, the close up of Robin's phone also shows her contact list to include Dan Blocker, TV's Hoss Cartwright from "Bonanza".
7. Ted says the famous architect Antoni Gaudi died after being hit by a bus. Gaudi was actually hit by a tramway in Barcelona, but the writers "adjusted" the story to accommodate the show, which takes place in New York, a city that doesn't have any land tramway lines.
8. During their discussion, Marshall compares GNB to the Galactic Empire in Star Wars and assumes that the architect of the Death Star is pretty psyched about his designed being flawed in the sense that a single bullet fired into a particular vent would explode the whole thing and that Ted wouldn't make that mistake. In Rogue One: A Star Wars Story, it is revealed that Galen Erso, the Death Star architect's, deliberately made the design flawed in order to get back at the Empire who took him away from his family.

Subway Wars

1. When Ted shows the gang directions to the steakhouse, the bar's address is 150 W 85th St. This is now 'Mannes College The New School for Music'
2. When Barney faked his heart attack he called out to Elisabeth. This is a reference to "Sanford and Son". Fred Sanford would clutch his chest and yell "I'm coming Elisabeth" when he pretended to have an attack. [Moderator: This should probably be under references but there was only a link to add movie references. This is a reference to a TV series]
3. Maury Povich can be seen in the background or is interacted by each of the gang memebers while running to the steak house.
4. While on the bus, Ted points out the Alberta Building to the man sitting next to him. This is the same building Ted identified as his favorite building in the city, and where the gang crashed the party of Jefferson Van Smoot in How I Met Your Mother: Robots vs. Wrestlers (2010).
5. Marshall really shouldn't have had too much trouble running 7 miles, as he had previously trained to run the New York marathon, which is more than 3 times the distance he had to run on this occasion.
6. "Marshall Versus the Machines", the folk song for Marshall's run, is sung by Jason Segel, the actor who plays Marshall.
7. Ted points out The Arcadian Hotel to the bus driver. This is the same building he must decide whether to save in S6:E23, "Landmarks".

Architect of Destruction

1. In this episode, Barney and Ted talk about old Guns n Roses vs the new Guns n Roses. The title is a word play on the Guns 'n Roses album "Appetite for Destruction"
2. When Zoey reads out the second sign it says ' it's always 4:20 somewhere' this is a direct reference to April the 20th (International counterculture holiday, where people gather to celebrate and consume cannabis).

Baby Talk

1. Lily's story about why she doesn't want to name her son Rob is a reference to the Pilot when she announced one of her kindergarteners got to second base with her.
2. When Marshall mentions the name Jeremy as a potential baby name, the song "Jeremy" by Pearl Jam plays during the flashback. The video for that song is parodied in the flashback when red paint is splashed on Lily.
3. Alyson Hannigan's character comes up with a list of baby names, one of which is Tara, the same name as her character Willow's girlfriend on Buffy the Vampire Slayer (1997).
4. When Lily stated that Marshal was writing checks her vagina couldn't cash, she was referring to the fact that she would have to deliver a large baby. However, some have viewed this as a mistake saying she meant her uterus, but that is incorrect.
5. The song that Marshall and his high school friends sing to the hot girl Tara uses the melody of song "End of the Road" by popular 90s R&B group Boyz II Men. Marshall was singing bass and holding a cane like Michael McCary from the group. Boyz II Men themselves (minus McCary) appear in the Season 9 episode "Slapsgiving 3: Slappointment in Slapmarra", after Marshall delivers the second to last slap to Barney (see "Slap Bet"), to sing their cover of Marshall's ode to slapping Barney, "You Just Go Slapped".

Canning Randy

1. The child that is driving Lily crazy in kindergarten is named "Johnny Marley". To punish him, Lily cuts the head off his stuffed horse, leaving it under his blanket at nap time. In the equivalent scene in the The Godfather (1972), the actor's name was John Marley.
2. The scene where Johnny wakes up with the head of his stuffed horse is a nod to The Godfather (1972).
3. The car alarm that Ted mimics to calm his class is the car alarm that Lily and Robin hear camping out for a wedding dress sale in 'Lucky Penny' (Season 2).
4. When they see Randy in the bar, his nose bleed switches nostrils from left to right and back again.
5. In Arthur's office, the picture of him and Tugboat behind his desk is the same picture on the wall behind Marshall.
6. First live appearance of Tugboat the dog. He previously appeared on a t-shirt.
7. At the Halloween party ted is dressed as a hot dog, Lily is dressed as a matador (bull fighter), Marshall is dressed as a bull, Barney is dressed as Johnny Lawrence from 'The Karate Kid' (whom he has stated to be his hero of the movie) and Robin is dressed as a nurse (although this is not a costume for Halloween as is revealed later).
8. Lily is drinking white wine at the Halloween party, but she's trying to get pregnant. In a previous episode, Lily mentions cutting alcohol, caffeine and sugar from her diet. Since they just tried again in the previous episode, it makes little sense for her to be drinking now, as she might have become pregnant and not know it yet.

Natural History

1. Lily says, "We'll make it work." to Marshall referencing the pilot when Marshall admits he loves olives.
2. When Ted shows the page of the newspaper about the Arcadia, the topic at the left side is about the place where Marshall and Lily live, "DOWISATRIPLA". And on the right side is a scoop about the "Cockamouse" from the 1st season. There is even a quote saying "No one is safe, not even your Mother.
3. When Ted is using the architecture of the building to whisper across the museum, this is actually possible. While it cannot confirm that this is possible in the New York museum that they were in, This is possible in The Union Terminal building in Cincinnati, Ohio which coincidentally is Cincinnati's History Museum. There are two water fountains on opposite sides of the dome in the entry way where you can speak across the crowded room as if you were right next to each other.
4. Arthur introduces the Captain as George Van Smoot. This is the same surname as Michael York's character in How I Met Your Mother: Robots vs. Wrestlers (2010).
5. When Barney and Robin are both touching the Egyptian statue, Barney begins to reach for his drink. When Barney does this it is clear that Robin spits her scotch back into her cup. She drinks the scotch in the next shot.
6. During the "anti-establishment" flashback, as Marshall and Lily mock Russell in his "monkey suit", Marshall is eating a very large "sandwich", which in How I Met Your Mother: How I Met Everyone Else (2007) was established as a euphemism for smoking a joint.
7. At the end of the episode, Ted calls Zoe 'Princess'. Jennifer Morrison would go on to star the following season as Emma Swan on 'Once Upon a Time' in which she was the princess daughter of Snow White and Prince Charming.

Glitter

1. Just before Barney turns off the Space Teens video the first time, the math problems Alan Thicke poses is 23 times 3. The answer, of course, is 69, further fueling the joke that Space Teens is porn.
2. At the beginning of Let's Go to the Mall, Robin says "come on Jessica, come on Tori!" In this episode we meet Jessica, however Tori is never introduced.

Blitzgiving

1. At McLarens, Zoey dares Marshall to send a picture of his junk to an anonymous person. Zoey calls for everyone to shout out random numbers to which "The Blitz" Jorge Garcia responds with 4 8 15 16 23 42, which were the numbers that Jorge Garcia's character, Hurley, discovers on Lost (2004).
2. When Steve "The Blitz" Henry describes being cursed by being the Blitz, he compares it to "being stuck on an island for ages." Jorge Garcia is most famous for his role on Lost (2004).
3. The method by which the curse of the 'Blitz' is passed from one person to another (a trail of mist going to and from the mouth) is a visual in-joke to the Buffy episode Buffy the Vampire Slayer: Hush (1999) where people magically lose their voices in an identical manner. In that episode of Buffy, the villains were called the Gentlemen, which is a catch phrase in this episode of HIMYM.
4. The voice who whispers "blitz" every time the curse is transferred is Josh Radnor, the actor who plays Ted.
5. The character name of the original Blitz is Matt Blitz. Matthew Blitz is one of the production staff for the show.
6. The character of "Matt Blitz" makes an appearance earlier in the show in the episode 'The Playbook'.
7. Ted says that he is "the Bueller" after Robin exclaims that Ted sang 'Twist and Shout' when the gang unexpectedly joined a Thanksgiving parade. This is a reference to Ferris Bueller's Day Off, in which the main character crashes a street parade and performs Twist and Shout. Marshal then quotes a famous line from the movie.
8. Zoey and the Blitz both appear together in season 2, episode 6 of Once Upon a Time as Emma Swan and Anton the giant.

The Mermaid Theory

1. Within the episode Zoey (who is married to the Captain) answers her phone by saying 'Ahoy'. It is implied that the captain makes her say this, however, Alexander Graham Bell (the man who patented the telephone) originally suggested that people answer the telephone by saying 'Ahoy'
2. Robin calls Marshall "Marsh Madness" as a nickname, however previously in the episode Bagpipes, we learned Robin hates nicknames, even in other people.
3. When Barney says: "Manatees City, where the grass ain't green and the girls ain't pretty" is a reference to Guns N' Roses song "Paradise City"
4. After The Captain knocks Ted's phone into the ocean he says "Can you hear me now?", a reference to the Verizon commercial.

False Positive

1. Barney says with his bonus check, he may get the Dibiase, which is a suit made of diamond pinstripes. Ted Dibiase was known as The Million Dollar Man in the WWF during the 80's.
2. There are a few theories as to why Lily wasn't actually pregnant: 1. Assuming that Lily was never actually pregnant in the first place, there are few reasons. For example: a) She may have had a phantom pregnancy, in a which a woman exhibits pregnancy-like symptoms when she's not actually pregnant. A real phantom pregnancy tends to be more common in animals than in humans, and in humans, it tends to be more psychological than physical. b) Lily could've simply misread and/or done the at-home test incorrectly, which resulted in a false positive. c) Whether or not she had done the at-home pregnancy test correctly, Lily could've also realized that those tests aren't always totally accurate, since she did make an appointment with her doctor to have an official test done to see if she was pregnant. d) Lily could've gotten her period, since women don't get their periods while they're pregnant (and a missed period is a common sign that a woman might be pregnant). 2. If Lily was actually pregnant in the first place but later turned out not to be, it's possible that she could've had a miscarriage--possibly even a chemical pregnancy. For those who don't know what a chemical pregnancy is, it's a very early miscarriage that happens before anything can be seen on an ultrasound--a sperm had fertilized the egg, but the egg itself ultimately fails to survive. It usually occurs at around the fifth week of the pregnancy.

Bad News

1. There is a countdown throughout the episode - from 50 to 1. The countdown is as follows: 50 - On a pamphlet in the Doctor's office in the first scene 49 - Same pamphlet on the Doctor's desk ("months later" according to Ted) 48 - Label on hot sauce Marshall uses at MacLaren's 47 - Barney's laser tag forms are for the "47th Annual" Laser Tag Competition 46 - Printed on Dr. Stangel's certificate behind Lily when they first meet 45 - 45¢ the price of the hot wings at MacLaren's 44 - Number of beers on tap, on a circular blackboard in MacLaren's 44 - (appears twice) Football number on a man's jersey in MacLaren's 43 - On the pamphlet Marshall is reading in Dr. Stangel's office 42 - Second side of the same pamphlet 41 - Race car poster number in Dr. Stangel's office (which disappears when Marshall goes back) 40 - Ted's book that "New York's 40 greatest landmarks" when Robin comes home from Day 1 39 - Number of office behind Robin 38 - On the back of Robin's co-worker's newspaper, 38° in the weather section 37 - Lily is reading a Decadence magazine with the "37 Recipes for Holiday leftovers" title on it. 36 - The number on Marshall's dad's beer, "Old Number 36" 35,34 - Stock markets are up 35.34 points on Robin's news screen 33 - Miners rescued from collapsed mine on Robin's news screen 32-27 - On Robin's screen: "Today's lottery numbers are 32 31 30 29 28 27" 26 - Marshall's dad is reading "26 Home Improvement Shortcuts" 25 - Textbook that Ted is reading in the apartment, "25 Greatest Bridges" 24 - One of Robin's co-workers is reading a magazine, with a sports player on the front with "24" on his jersey 23 - Metro News 23, the channel Robin says "I'm a dirty, dirty girl" on 22 - Seen in the corner of Robin's Japanese broadcast 21 - Calendar behind Dr. Stangel 20 - Room for masturbation room at Dr. Stangel's office 19 - "Top 19 Nekkid girls countdown" on Nekkid magazine in the room 18 - Apartment number of Marshall and Lily's apartment 17,16 - Marshall's specimen cup seen in his apartment 15 - Grams of fiber in Robin's cereal 14,13 - Apartment number of Sandy's apartment 12 - The book "12 days of Christmas" behind Marshall when he's speaking with his parents in their apartment 11- On Ted's architecture book, "America's 11 greatest water towers" 10 - On Robin Sparkles left jacket arm when shown to co-workers by Robin 9 - Disguised Barney holds a folder when talking to Marshall 8 - Number on Dr. Stangel's door 7 - Number on Marshall's champagne bottle 6 - Dr. Stangel turns the folder with the 9 on it upside down 5 - Barney gives Marshall a "Fertility 5" 4 - The "4 Layers of the Uterus" poster in Dr. Stangel's office 3 - "Open til 3 am sign" outside MacLaren's 2 - Clock in Marvin Sr's wood shop 1 - Number of the cab Lily arrives in
2. The glasses Barney is wearing in Dr. Stangel's office are The Sensory Deprivator 5000 that Ted invented in the season 2 episode Monday Night Football.
3. Neil Patrick Harris is credited twice for this episode, once in the opening as a member of the main cast and once at the end as "Dr. John Stangel."
4. In the episode "Bad News," the only number that does not appear onscreen as a numeral is the number 5. Instead, between the numbers 6 and 4, Barney and Marshall share a high five.
5. In the episode Bad News there is a hidden countdown 1-50 that leads to the bad news but the number 44 is shown twice in a row.
6. At the beginning of the episode on the calendar of the doctor a 50 is noticeable. Throughout the episode is a countdown from 50 to 1 until Lily talks to Marshall at the end, e.g. "48" on the sauce in Marshall's Hand, and "36" on his father's beer can.
7. During the shooting of the cab scene, Jason Segel's (Marshall) script didn't tell him the real news, but instead it said the Lilly was going to say she was pregnant. Therefore, Marshall's reaction is actually Jason Segel's very real reaction. The producers of the show did this because the show focuses on milestones of young adult life, and they wanted to make the shock and dismay of unexpected events such as that scene very real.
8. The script for the episode "Bad News" originally had the twist written as Lily being pregnant. It was only on the actual day of shooting that the writers revealed to Jason Segal and Alyson Hannigan that the ending would be different, and even then, it was only Alyson who knew the final scene. She and Jason worked out that he would react when she said the word "it", which turned out to be the end of the sentence "He didn't make it". Until that moment, Jason had no idea what he would be reacting to. What you see in the episode is the one and only take they shot of his reaction.
9. According to the episode's commentary, Jason Segel's line "I'm not ready for this," after hearing about his dad's death, was improvised.
10. The number 2 of the countdown appears on a clock, referencing the series statement that "Nothing good happens after 2 a.m", from Season 1.
11. In the closing moments of the episode Marshall finds out the his dad has passed away. Through-out the episode there is a subtle countdown to the moment Marshall hears the news on objects through out the scenes. The countdown starts at 50 on a calender and goes all the way down to the number of the taxi(0001) that Lily arrives in to tell Marshall the news. Some other numbers include: The number 11 on the front of an architecture book, the price of 45 cents for buffalo wings, the conference room Robin has a meeting in is 39 and Lily and Marshall's apartment number is 18.
12. There are numbers hidden within scenes throughout the episode that count down to Marshall hearing the news of his father's death. The numbers start at fifty and count down to one. E.g. the taxi cab number, the number on the pregnancy brochure, the apartment number of Marshall and Lily, the date on a calender, the number on Marshall's semen sample container.
13. In the episode 'Bad News' season 6, episode 13, numbers are seen 'hidden' throughout the show starting at 50 going down to 1 which is seen on the taxi cab Lily pulls up in to tell Marshall the bad news about his father.

Last Words

1. A funeral-goer says to Robin, "I hear you're a woman who can get things." And she replies, "I've been known to locate certain items from time to time." This is a reference to the exchange between Red and Andy Dufresne in The Shawshank Redemption (1994).
2. Danny Strong who plays Trey in this episode also starred with Alyson Hannigan in Buffy The Vampire Slayer as Jonathan.
3. The pill that Robin gives Lily is most likely Adderall. Adderall is a stimulant prescribed for the treatment of ADHD and can cause people to feel energetic and invigorated. Robin also tells Lily to stay hydrated, which is a known side effect of Adderall.
4. Ted and Barney's idea to help Marshall by showing him funny videos is a reference to the fact that Bob Saget who voices older Ted was the first host of America's Funniest Home Videos.

Oh Honey

1. Marshall uses cards from the board game "Clue" in order to explain the relationship of Zoe and Ted to his mother and brother. Throughout the episode, the characters appear in clothes colored according to the characters from "Clue" which Marshall uses. Ted is Professor Plum, Zoe is Mrs. White, Honey is Miss Scarlet, Barney is The Reverend Green and Marshall refers to the Captain as Colonel Mustard.
2. When Barney passes Zoey on the street, he's carrying a silver briefcase. However, if you look closely you will notice that he is actually handcuffed to the briefcase. The episode never explains why!
3. All of Ted, Barney, and Zoey's outfits throughout the episode fit with their 'Clue' character counterparts.
4. Honey (Katy Perry) mentions at the beginning of the episode that she is going to be on 'Lost' (2004-2010). Five episodes earlier Jorge Garcia, who plays a central character on 'Lost', appeared as Steve The Blitz on this show.
5. Katy Perry (Honey) is the fourth star from Smurfs (2011) that has appeared in How I Met Your Mother. Neil Patrick Harris (Barney) starred in it as well as: Jayma Mays (Coat Check Girl in season 1 episode 5, Okay Awesome) and Tim Gunn (in season 5 episode 12, Girls versus Suits).

Desperation Day

1. The shirt that Marshall wears throughout the episode says 'Tarkenton Physical Education' on it. Fran Tarkenton was the quarterback for the Minnesota Vikings for most of the 60s and 70s where Marshall is from.
2. Nazanin Boniadi, who plays Barney's love interest - Nora, was a Scientologist. She was 'selected' to be Tom Cruise's potential wife. She spent some time with him and got close. Then, a senior member of Scientology came to visit. Nazanin was unwell and didn't give the best impression of herself. The relationship ended swiftly after that. She was apparently heartbroken. She has gone on to find success in Homeland.
3. When Lily visits Marshall in St. Cloud Minnesota he asks his mom if she bought AA batteries because he is on a "sick Dr. Mario Run" he is playing this on an original game boy and switching out the batteries would automatically end his game by turning off the game boy
4. British morning socks do exist, though they're more commonly known as slipper socks. They're a thick pair of socks, with either a double layer sole or non stick material added in a pattern. They're often taken to hotels or overnight stays where you might not want to walk around barefoot on strange (or cold) floors, but don't want to pack bulky slippers from home.

Garbage Island

1. When asked how Ted met Zoe, he begins with "Once Upon A Time..." Jennifer Morrison, who plays Zoe, would go on to star in the ABC show, Once Upon A Time.
2. It can be seen on the coffee mug Robin is holding while talking to Barney, is from Tim Hortons, the popular Canadian coffee shop. Cobie Smulders and her character Robin are from Canada.
3. Last appearance of the character Wendy, the waitress at MacLaren's. The beginning of the episode flashes-forward to 2021, when she and Ted meet again in a Hong Kong airport.

A Change of Heart

1. Incorrectly regarded as goof: In the scene that explains Marshall's calzone incident, which takes place in 2006, Barney has an iPhone 4, which wasn't released until 2007. However, due to Barney's high-paying and unexplained job, he tends to have a lot of crazy "futuristic" gadgets, so it's reasonable to assume he was beta testing the phone, or he got it from one of his mysterious sources, which would explain him having the phone earlier than it was released.
2. This episode features Robbie Amell playing a dog-like character named Scooby. He had previously played Fred in two live action Scooby- Doo movies.
3. The doctor seen checking Barney is actress Suzy Nakamura who also plays a doctor in Modern Family in various episodes.

Legendaddy

1. This episode is Barney's first interaction with his father. The episode is season 6 episode 19 (6x19). Father's Day in 2011 was June 19th (6/19).
2. John Litgow and Neil Patrick Harris were both nominated for the Golden Globe Award for Best Actor in a Supporting Role in a TV series in 2010, which Litgow won for his performance in Dexter.
3. When Barney retells the night out with his father, Jerome, he says that back in '83 Jerome was lugging amps for the Stones through West Germany. Whenever Barney lies he always uses the number 83. This means that the story he is telling is a lie.

The Exploding Meatball Sub

1. Robbie Amell plays Scooby as a reference to Scooby Doo. Robbie plays Fred in the TV movie of Scooby Doo.
2. In the final skit, the stain on Barney's pajamas disappears and reappears.
3. Barney mentions to Marshall that "you can't pay your mortgage with Hackey Sacks..." Later in the series, when meeting Marshall anda Lily's college friend, they may have been able to do that with the royalties that Seth Greene's character was going to give him from the proceeds from "The Three Hack-Migos."
4. In the '10 years later' Robin and Barney are shown without weddings rings, foreshadowing all future engagements and marriages break up by then

Hopeless

1. When Barney goes up to Jerry on the dance floor to suggest he stop dancing, Jerry (played by John Lithgow) says "Sorry, small town preacher from the mid-west, is there a law against dancing?". This is an inside joke reference to the movie Footloose (1984), which portrays a small mid-west town where dancing has been outlawed for moral reasons, a movement spearheaded by the town preacher, played by John Lithgow.
2. When Marshall is talking about his playwright "works" he mentions a rock opera. This is reference to Jason Segel's rock opera in Forgetting Sarah Marshall.
3. The shirt that Robin's crush (Nick) is wearing in the flash back of the close out sale is the same shirt that one of the GCWOK's was wearing in Season 3, Episode 19 "Everything Just Go"
4. The show's opening theme song and the photos displayed during it differ in only four episodes throughout nine seasons. How I Met Your Mother: Hopeless (2011) shows the main characters playing various instruments, How I Met Your Mother: Bedtime Stories (2013) is played to the tune of a music box, How I Met Your Mother: 46 Minutes (2012) excludes Lily (Alyson Hannigan) and Marshall (Jason Segel) after they move to the suburbs with new photos of Ted (Josh Radnor) and Robin (Cobie Smulders) looking annoyed with Barney (Neil Patrick Harris) and How I Met Your Mother: How Your Mother Met Me (2014) shows Tracy (Cristin Milioti) with several of her friends. How I Met Your Mother: 46 Minutes (2012) has a second version later in the episode to a Russian theme with Stripper Lily and her boyfriend.

The Perfect Cocktail

1. As of this episode, Barney had slept with 282 women.
2. During the absinthe cut scene, Marshall says they have water, soda, or purple stuff. This is a reference to an old Sunny Delight commercial.
3. The song heard at the end of the episode, when Lily and Robin are claiming their booth back, is an guitar version of Summer Love by Justin Timberlake.
4. The music heard in the background of the bar when Marshall almost gets in a fight with his mirror self under the influence of Gin is the same music from Okay, the club in S1E05 "Okay Awesome"
5. When Marshall touches the "mirror" after running into it, his left thumb disappears.
6. Josh Radnor, Ted, was actually beatboxing during the flashback of him "under the influence of bourbon." Josh is actually a really talented beatboxer.

Landmarks

1. Least viewed episode.
2. Ted's mom, in his dream, has a top spinning, likely a reference to Inception (2010) and the main character's tool to know if he was dreaming. The spinning top proves he is in a dream.
3. When Ted looks at the Arcadian he says "Look on my works, ye mighty, and despair!" This is a line from Percy Bysshe Shelley's poem "Ozymandias."
4. The outside of the building where the meeting of the Landmarks Preservation Commission took place it's also the outside of Barney's building (as seen in Season 7 Episode 20)
5. When Ted goes to say that the Arcadian should not be a landmark, he is holding in his hand the little airplane that Barney gave him in How I Met Your Mother: Unfinished (2010).

Challenge Accepted

1. The diner located on the bottom floor of The Arcadian is called the Royal Diner, which has the same name and exterior as the diner featured on the show Bones.
2. The soup shop at the beginning of the episode is the same shop used for the Soup Nazi on Seinfeld.
3. Barney's line at the end to Nora about it being too late for sundress is a reference to an earlier episode that season when he complains to Ted at the bar about it being too late in the year for girls to wear sundresses.
4. In the Season 6 finale, you can see The Royal Diner from the show Bones attached to the Arcadian- which they later demolish for the new GNB headquarters that Ted designs.