How I Met Your Mother

Like Barney Stinson and suits, How I Met Your Mother and music fit well. So co-creator and executive producer Carter Bays thought it's appropriate for the CBS sitcom to mark its 100th episode with a big, splashy musical number.

"I don't think we're going to do too often, but now that we've gotten our feet wet, we'd love to do it again," Bays said.

Watch a sneak peek of the musical number

Titled "Girls vs. Suits" and airing Monday at 8/7c, the episode features the musically inclined cast performing Barney's ode to suits, "Nothing Suits Me Like a Suit," backed by 65 dancers and to the strings of a 50-piece orchestra — bigger and badder than any Slap Bet jingle or Robin Sparkles music video before it.

Bays wrote the song with co-creator and executive producer Craig Thomas, with whom he also composed the show's theme song with their band The Solids. The "Nothing Suits Me Like a Suit" number — a showcase for resident song-and-dance man Neil Patrick Harris — plays out in Barney's mind when he's forced to choose between his signature two-piece gear and a hot bartender (guest star Stacy Keibler), who disdains men in suits.

"The whole concept of this was to have an on-air 100th episode celebration party and just [go] nuts and have three minutes of unadulterated, joyful fun and ... just kind of share our joy and pride in 100 episodes and throw a little party for the fans," Thomas said.

Sartorial god Tim Gunn also guest-stars to help Barney, well, make it work.

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"[Gunn] was every bit the wonderful man you think he's going to be. I want him back in every episode," Alyson Hannigan said. "I've never seen people that happy about a guest star. He was more popular than Britney Spears. That's saying something."

Hitting the three-digit milestone is saying something too for the time-jumping sitcom that had to wait until the eleventh hour for renewal in its early seasons. Five seasons later, it boasts an Emmy nomination for comedy series, endless flashbacks and dozens of zany but thoughtful story lines. It's been interesting to see how the show has evolved, Thomas said.

"Because we're so flashback-happy, we can kind of dive back into those things and really get to know these people in ways that in 20 minutes in one pilot you never would've expected," he said. "How could you have predicted [in the pilot] that somehow not far over a year later, Barney would be on the set of The Price Is Right ... so he could tell his father Bob Barker that he was his son? ... It's the most fun thing in the world to discover that kind of stuff, discover new details of their past and personalities and find ways to intersect the characters."

Rachel Bilson appearing on How I Met Your Mother — as the Mother?

One thing — or character, rather — that hasn't been unveiled yet is, of course, the titular Mother. In the 100th episode, though, Ted (Josh Radnor) will get the closest he's ever been to meeting his wife after befriending Cindy (guest star Rachel Bilson) at Columbia University, where he works. Fans will be "teased, but pleased" with the new offering of clues, Hannigan said.

Bilson was only attached for one episode. "She is very important to the ultimate story, so she probably will come back," Bays said.

Bays and Thomas say they're still committed to their "leading plan" of unraveling the mother's identity, but don't feel any pressure because for every person who wants to know, there's someone who doesn't want to know yet.

Carrie Underwood to guest-star on How I Met Your Mother

"Then it is like the ride's over in a lot of ways [if we reveal her before the series is over]. We definitely have ideas for stories that could take place after you've met the mother," Thomas said. "[But] in addition to Ted, we've got four other very interesting characters and we sort of like the idea of making the show about more than just that one central question."

Are you excited for the 100th episode? What are your favorite Mother episodes?