The How I Met Your Mother cast doesn't shy away from celebrations.

For its 100th episode January 11, the CBS comedy will feature a grand musical number featuring its five stars, 65 dancers and a 50-person orchestra.

"It almost felt like an old-school MGM musical to me. It was a lot of cast and crew grouping together to make it special," says star Neil Patrick Harris.

Harris, Josh Radnor, Jason Segel, Alyson Hannigan and Cobie Smulders will perform a 2½-minute song-and-dance piece: "Nothing Suits Me Like a Suit."

The show has provided musical number before - Robin's 'tween videos and Marshall's piano prelude to a slap come to mind - but nothing this elaborate.

HIMYM producers Carter Bays and Craig Thomas wrote the words and music, then recruited composer John Swihart and choreographer Zach Woodlee (Glee).

IT SUITS THEM: How I Met Your Mother turns 100 and pays tribute to Barney's attire.

"The way we viewed it was our 100th episode would end with something that felt like a party, like an on-air party for fans, and create a jubilant celebration moment at the end of the show," Thomas says. "It feels like a crazy movie fantasyland."

Harris is just happy Thomas and Bays wrote it: "I'm glad we didn't source it out. It has the same sense of humor and sort of obscure comedic ring to it."

In the episode, "Girls vs. Suits," the always-suited-up Barney has the chance to date a hot bartender, but there's a catch: She disdains men in suits. Thomas describes the musical extravaganza as "kind of a love song to The Suit, capital T, capital S."

It will also reveal more, Thomas says, about the "mother," Ted's eventual wife: "It's the closest we've seen Ted get to answering the question: 'Who is the mother?'"

Rachel Bilson guest stars in the episode. Hmm. We're just saying.

Steve Marsi is the Managing Editor of TV Fanatic. Follow him on Google+ or email him here.