How I Met Your Mother premiered 10 years ago this week. After nine seasons, most viewers were so focused on the series's polarizing finale that they almost forgot how sneakily innovative the multi-camera sitcom with the multiple flashbacks and flash-forwards was in 2005. Here are some facts about the show, as approved by the Slap Bet Commissioner.

1. TED, MARSHALL, AND LILY ARE BASED ON REAL PEOPLE.

When college friends and Late Show with David Letterman writers Carter Bays and Craig Thomas were invited to pitch a network series, they flashed back to 1997, when Bays spent a lot of his time at Thomas's apartment, which he shared with his longtime girlfriend (now-wife) Rebecca, complaining about about being single. In the script, Bays became Ted, Thomas became Marshall, and Rebecca became Lily. Real-life moments like Bays inviting someone to a wedding without realizing he didn’t have a plus-one, or calling Rebecca a “bitch” during a brief breakup with Thomas were written into the series.

2. JIM PARSONS AUDITIONED TO PLAY BARNEY.

Parsons said the description for the Barney Stinson character read “a big lug of a guy." "I got it and was like, 'Who the hell looked at me and thinks 'big lug of a guy?,'" Parsons recalled. "It wasn’t offensive, I thought, 'This is silly.'" The future The Big Bang Theory star auditioned anyway, but lost out to Neil Patrick Harris, who credited the physical comedy he exhibited trying out for producers, and later for CBS president Les Moonves, for landing the role. Specifically, when asked to pretend to be playing laser tag (like Barney would later do), Harris started a dive roll that ended with his body meeting a chair. In 2008, Harris said he believed Barney was 60 percent Larry from Three’s Company.

3. SCOTT FOLEY WAS OFFERED THE ROLE OF TED, AND JENNIFER LOVE HEWITT WAS OFFERED ROBIN.

Hewitt turned down Thomas and Bays’s offer to star on another CBS show, Ghost Whisperer, instead.

4. MACLAREN’S, THE GANG'S FAVORITE BAR, WAS NAMED AFTER A PRODUCTION ASSISTANT.

Carl MacLaren worked as an assistant to the producers for two years before being promoted to associate producer. The bar itself is based on the New York City bar McGee’s, where Bays and Thomas hung out during their time writing for Letterman.

5. THE "HAVE YOU MET TED?" PICK-UP LINE WAS FROM BAYS AND THOMAS’S BOSS AT LETTERMAN.

Late Show co-head writer Justin Stangel invented the pick-up line. When Stangel and Bays were at a bar (usually McGee’s), Stangel would stop a girl walking by and say, “Have you met Carter?” Barney Stinson and several other characters ended up using the line throughout the series.

6. THERE WAS NO STUDIO AUDIENCE DURING FILMING.

Shooting of the multiple scenes (the pilot had 60) took place over three days. After that, an audience watched the episode, and their laughter made it into the laugh track.

7. JASON SEGEL’S SMOKING WAS A PROBLEM FOR ALYSON HANNIGAN.

Hannigan (Lily) was upset over having to kiss her on-screen boyfriend-turned-husband Segel (Marshall) because it was like “kissing an ashtray.” Segel managed to quit for a year, but stress caused him to start up again.

8. THERE WAS A REAL WEDDING PROPOSAL ON THE SHOW.

On the season two finale “Something Blue,” restaurant scene extra Timothy Russo proposed to his girlfriend, fellow extra Jana Rugan, in the biggest surprise of Rugan’s life. During rehearsals, an actor took the ring from Robin to finish the scene, which is what Rugan thought would happen when the cameras started rolling. Russo’s brother’s friend, staff writer/producer Matt Kuhn, helped with planning the whole thing.

9. BRITNEY SPEARS WANTED TO BE ON THE SHOW.

Specifically on the episode “Ten Sessions,” which freaked out Bays and Thomas, who were worried that the singer would want to play Stella, a character for whom they had big plans. Instead she liked the role of Stella's receptionist, Abby. The episode was the most-watched episode at that point in the 18-to-49 year old demographic, and was credited with possibly saving the show from cancellation.

10. ALICIA SILVERSTONE WAS ORIGINALLY GOING TO PLAY STELLA, UNTIL BRITNEY SPEARS GOT INVOLVED.

Silverstone had to be replaced by Sarah Chalke after Silverstone’s representatives worried that their client would be overshadowed by Spears.

11. COBIE SMULDERS WAS DIAGNOSED WITH OVARIAN CANCER DURING THE THIRD SEASON.

Smulders received the bad news at the age of 25, and kept it a secret from the public. Two years—and several surgeries—later, she was declared cancer-free. Earlier this year, she opened up about her illness for the first time in order to create more awareness about the disease, particularly for young women.

12. THE CAST’S SIGNIFICANT OTHERS PLAYED ASSORTED WEIRDOS.

Alyson Hannigan’s husband Alexis Denisof (the two met on Buffy the Vampire Slayer) played vain news anchor Sandy Rivers in 10 episodes. Smulders’s husband Taran Killam played Gary Blauman, both before and after he started on Saturday Night Live. Harris’s husband David Burtka portrayed Lily’s high school boyfriend, Scooter.

13. CONAN O’BRIEN APPEARED AS AN EXTRA.

O’Brien won a charity auction to be a background actor in an episode. Bays and Thomas wanted to give the late night talk show host a much bigger part in 2012's “No Pressure,” but O’Brien decided it would be funnier—and more realistic—if he was just an extra.

14. TED’S KIDS KNEW THE ENDING OF THE SERIES FOR NINE YEARS.

Lyndsy Fonseca (Penny) and David Henrie (Luke) shot all of their scenes during season one, because Henrie was going through puberty. When the kids's footage for the series finale was shot, Thomas and Bays were the only people present. Fonseca and Henrie also had to sign a confidentiality agreement. The two honored it, even after Henrie was bribed with alcohol at bars by strangers wanting to know what he did.

15. VICTORIA WOULD HAVE BEEN THE "MOTHER" IF CBS CANCELED THE SERIES EARLY.



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The initial 13-episode order conveniently concluded with “Drumroll, Please,” which introduced Ashley Williams’ character.

16. JOSH RADNOR KEPT THE BLUE FRENCH HORN.

Bays and Thomas agreed to split custody of the iconic prop, but the actor who played Ted Mosby “humbly and sweetly” asked for it. "And folks, when Ted Mosby comes and asks you for the blue French horn, ya give him the blue French horn," Thomas said. "It felt right."

Neil Patrick Harris took home Barney’s playbook and the group’s MacLaren’s tabletop, Smulders got Robin Sparkles’s denim jacket, and Hannigan acquired the little British phone booth.