"How I Met Your Mother" ran for 9 years, but plenty of its recurring jokes started on season 1.
The mother's name, the cocreators, and cast members' spouses all pop up on the first season.
Warning: This story contains major spoilers for all seasons of "How I Met Your Mother."
Ted's children are dressed differently for the pilot than they are for the rest of the series.
Since Ted is meant to be telling his children the story of how he met their mother over the course of one long conversation, his son and daughter are shown wearing the same clothes throughout almost every episode.
The one exception is the pilot, where the daughter is wearing a gray cardigan, skirt, and tights, and the son is wearing a dark polo shirt and jeans.
For the rest of the series, Ted's daughter wears a pink cardigan, shirt, and pants, and the son wears a shirt, hoodie, and jeans.
The background behind the children is also a little more cluttered after the pilot episode.
Barney is interested in Robin the first time he sees her.
When Ted points Robin out the first time he sees her at MacLaren's, Barney immediately makes a lewd comment about her.
He seems to show interest in her throughout the first season, utilizing his usual flirtatious nature.
Barney's clear interest is significant for fans who know later plot points of the show.
The decor in the bar changes between the first and second episodes.
MacLaren's Pub, where the friends spend a lot of time throughout the series, has far less wall decor on the pilot than it does for the rest of the series.
There are more signs and neon lights added near the windows and in the back corner of the bar between the first and second episodes.
Marshall references "The Great Gatsby" when Ted keeps throwing parties for Robin.
Ted throws parties three nights in a row as an excuse to invite Robin over.
Marshall alludes to F. Scott Fitzgerald's "The Great Gatsby" by comparing Ted to the titular character.
In the book, Jay Gatsby throws extravagant parties every weekend to catch the attention of one particular woman.
Ted says he and Barney are the same height — and he's almost right.
Ted says that he and Barney are the same height on the second episode.
When Neil Patrick Harris, who plays Barney, and Josh Radnor, who plays Ted, stand next to each other, it's clear they're really close to the same.
Barney and Ted make seemingly impossible calls on a plane.
While attempting to pick up girls at the airport, Barney and Ted get on a flight to Philadelphia.
They call Marshall from the plane to ask him to pick them up.
Both times they make calls, the plane is apparently in the air, so calling Marshall on their flip phones shouldn't be possible.
Natalie has a sock monkey with a "Happy Birthday" sweater.
Ted broke up with Natalie on her birthday, twice.
When listing things he likes about her, he mentioned her sock-monkey collection.
At the end of the episode, one of the sock monkeys that can be seen on her bed is wearing a "Happy Birthday" sweater.
Two of Jason Segel's "Freaks and Geeks" costars appeared on the first season.
Before "How I Met Your Mother," Jason Segel, who played Marshall, appeared as Nick Andopolis on NBC's "Freaks and Geeks."
Levine appeared as one of the people waiting to get into the club on episode five, and Starr played a guy Robin had a bad date with on episode eight.
Robin says she never played any team sports, but she was on a hockey team.
When Robin struggles to embrace her new relationship on the season-one Halloween episode, she mentions that she's never played a team sport. She claims she only played tennis.
But this is contradicted on later seasons when Robin is shown playing hockey, which is a team sport, in flashbacks.
Radnor breaks and laughs during the matchmaker scene with Harris.
Barney tags along when Ted decides to sign up for Love Solutions, a matchmaking service.
While Harris, as Barney, is lying to the matchmaker about what he wants in a relationship, Radnor, as Ted, can't keep a straight face.
The camera cuts away and shows Ted with a serious expression, so it seems like Radnor was actually supposed to look annoyed the entire time.
Ted's alarm clock seems to have the wrong time.
The morning that Ted wakes up next to Trudy and a mysterious pineapple, his alarm clock seems to have the wrong time.
Ted mentions that it's morning, and everyone else is drinking coffee or still asleep. But the alarm clock visible on his nightstand shows the time as 12:53.
Presumably, that would mean it was actually afternoon or the middle of the night.
Sandy Rivers is mentioned several episodes before his first appearance.
Robin has to work during Claudia and Stuart's wedding when another anchor isn't able to come in.
When her job calls, she asks what happened to Sandy before agreeing to work that night.
Six episodes later, Sandy Rivers appears onscreen for the first time as her coanchor.
Lily's paintings can be seen in Marshall and Ted's apartment before she officially moves in.
At the start of season one, Lily has her own apartment even though she almost always stays over at Marshall and Ted's.
Lily's paintings can be seen throughout their apartment before she officially moves in midway through the season.
In fact, one of the paintings usually displayed over Marshall and Ted's fireplace can later be seen in Lily's apartment when she officially moves out on season two.
Barney's old zine was named "Brainbows."
Before Barney became a suit-wearing womanizer, viewers find out he was an optimistic barista who made his own zine (small, self-published publication) during a flashback.
The zine is titled "Brainbows" and has a peace sign on the cover.
The subhead on the cover reads: "Taking global action against global warming" with a recycling symbol.
The anthropologist Marshall looks up to is fictional but likely based on a famous conservationist.
In another flashback, fans find out Marshall's idol when he was younger was Dr. Aurelia Birnholz-Vazquez, an anthropologist who wrote "Life Among the Gorillas."
Although she's not a real person, her character may have been inspired by Dian Fossey.
Fossey studied gorillas for decades as a conservationist and made significant progress in calling for the protection of gorillas from poachers.
When Barney talks to Lily's class, there's a disclaimer about him on the chalkboard.
Robin and Barney both visit Lily's kindergarten class to talk about their jobs on Career Day.
Since Lily doesn't know what Barney's job is, his name is written on the chalkboard instead of his profession.
She wrote, "Barney (not the purple one)," to distinguish her friend from the famous TV dinosaur. But seeing as Lily teaches kindergarteners, it's a little unlikely they'd be able to read and comprehend the note.
Barney successfully does a magic trick that he messed up earlier on the season.
Harris brought his real skills as a magician to Barney's character and can be seen doing various magic tricks throughout the show.
Early on the first season, he attempts to do a fireball trick and singes his hand.
When he does what appears to be the same trick again in front of Lily's class, he performs it successfully.
Ted's favorite book outlines the main romantic plot of the show.
Ted mentions his favorite book, "Love in the Time of Cholera" by Gabriel García Márquez, several times while describing his dream girl.
The book tells the love story of a couple that eventually gets together again after years of being apart. One of them even ends up marrying someone else who dies in the interim.
This is very similar to Robin and Ted's will-they-won't-they plot throughout the series.
The connection between the two stories is further cemented when Ted is seen reading the book at the train station on the last season.
The cocreators of the show appear as fake paramedics when Barney tests a pickup line.
When Barney is trying to get a woman's phone number, he has Wendy, the waitress at MacLaren's, and two actors posing as paramedics help him stage a scene.
Ted trips on the roof immediately after it starts raining.
On the season-one finale, it starts raining after Ted spends hours attempting to do a rain dance.
Ted jumps and cheers, but while he's jumping, he visibly trips over part of the roof and starts to fall.
The scene cuts away before he's finished falling, but he clearly moves his arms to catch himself.
The real husbands of multiple cast members appeared throughout the first season.
Alexis Denisof, David Burtka, and Taran Killam are all married to different members of the main cast, and they each played recurring characters who first appeared on season one.
Denisof is married to Alyson Hannigan (Lily) and plays Sandy Rivers.
Harris' husband Burtka plays Lily's high-school ex-boyfriend Scooter.
Killam, who's married to Cobie Smulders (Robin), plays one of Barney and Marshall's coworkers, Gary Blauman.
The mother's name was secretly revealed on season one.
Toward the end of the show, fans discover that Ted's wife, and the mother of his kids, is named Tracy McConnell.
But the name Tracy pops up long before the mother ever appears on the screen.
On season one's Thanksgiving episode, Ted meets a stripper who says her name is Tracy.
When Ted jokes to the kids that this is how he met their mother, they're shocked — possibly because they believe him for a moment because Tracy is actually their mother's name.
Since Bays and Thomas filmed the final scene with the kids early in production for continuity reasons, it's possible they had the mother's name picked out all the way on season one.
Look for the small details in "How I Met Your Mother" by streaming all all 9 seasons on Hulu:
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