But there are quite a few things that happen behind the scenes of this hilarious show

that you probably don't know about.

Welcome to Trending 10.

And today we're counting down the top 10 things

that you probably didn't know about How I Met Your Mother.

Ready? Because here we go.

Many of the cast significant others appeared as extras on the show.

But it's a little inside joke the significant others were only allowed to play bizarre characters.

For example, Alyson Hannigan's husband played the weird Newscaster, Sandy Rivers.

Cobie Smulders's husband appeared as Gary Blauman

and Neil Patrick Harris's husband played Scooter, Lily's high school boyfriend.

On-screen couple Lily and Marshall had a little bit of drama during filming.

Marshall was played by Jason Segel who had a smoking problem at the time of filming

and Lily's actress Alyson Hannigan hated kissing seagal on screen

because it was like kissing an ashtray.

Segal managed to quit for a year, but eventually picked the habit back up.

The original cast of the show look very different from what we know today.

Originally Scott Foley was planned to play Ted

and Jennifer Love Hewitt was planned to play Robin.

(S)he would eventually turn down the role

so she could be on the new CBS show "Ghost Whisperer"

which unfortunately didn't go too well for.

There was a lot of confusion around the character Stella.

Pop star Britney Spears had expressed interest in being on the show

but the producers were actually worried that Spears would want to play Stella,

a character that they had big plans for and did not want Spears to play.

Luckily, Spears was more interested in playing Stella's receptionist, Abby.

The episode that Britney Spears appeared on, titled Ten Sessions, went on to be the most popular episode of the time

and ended up saving the show from cancellation.

Stella was then planned to be played by Alicia Silverstone.

But after Spears was recruited to play stella's receptionist,

Silverstone's representatives made her pull out of the show

in fear that her performance would be overshadowed by Britney Spears.

Eventually Sarah Clarke was signed on to play Stella,

and she ended up being the great final choice.

Penny and Luke had to film their scenes at the end of the show nine years early.

Fearing that the kids would go through puberty before the ending of the show,

the crew had to film Penny and Luke scenes in the finale

all the way back during season one of the show.

The two kids even had to sign a confidentiality contract which of course they honored.

And nine years later the world got to see the scenes

that the kids shot all the way back in season one.

Most sitcoms are recorded in front of a live studio audience.

But the pilot episode of How I Met Your Mother was actually recorded in a regular studio without an audience.

In fact the pilot episode took a whole three days to film

as there were far more scenes in the production team expected.

Once the episode was finally finished, it was shown into an audience

whose laughter was recorded and added to the sound mix of the pilot before aired.

Did you know that Conan O'Brien actually appeared on the show?

But he didn't appear in the way you might think.

You probably expect someone of Conan's caliber to have a lead role.

But believe it or not, Conan actually entered a charity auction to be an extra on the show and won.

After winning the auction, the producers of How I Met Your Mother wanted to give Conan a larger part

but O'Brien declined the offer.

Thinking that it would be much funnier if he was just somewhere in the background,

so on the episode "No Pressure" Conan appears in the background as a regular extra.

The gang likes to hang out at the bar Maclaren's.

But there's more real about this bar than you probably know.

The name comes from Carl McLaren

who worked as an assistant to the producers of the show for two years before How I Met Your Mother started production.

The actual bar is based on a New York City bar called McGee's

where the producers hung out while working on their previous show "Letterman" (Late Show with David Letterman).

Did you know that there was a real proposal on the set of the show?

During the filming of the season two finale,

one of the extras in the restaurant scene Timothy Russo proposed to a fellow extra Janna Rügen.

Russo's Brother's friends was one of the writers for the show and managed to help organize the entire thing.

Perhaps the most memorable character on the show is of course Barney played by the legendary Neil Patrick Harris.

But did you know that Neil wasn't actually the first choice for the character?

Barney was originally supposed to be played by Jim Parsons who many know is Sheldon on the Big Bang Theory.

However, had auditioned for the show, Parsons was beat out by Harris for the role

and a good thing he did. If things had gone differently,

Barney would not be the character we know and love today

and the Big Bang Theory likely wouldn't have Jim Parsons as Sheldon.

So we'll just call it a happy incident.

But there we go guys, that's it for our list of 10 things you probably didn't know about the hit TV sitcom How I Met Your Mother.

Got any other sitcom facts, you should have let us know down in the comment section below.

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