‘The Flash’ Musical: Executive Producer Andrew Kreisberg Previews the Crossover Episode

When it comes to “The Flash,” it wasn’t really a case of if the CW show would do a musical episode, but when.

The cast of the show, which is midway through its third season, is loaded with actors with a great deal of song and dance experience: When you have a “Glee” alumnus (Grant Gustin) and an original “Rent” cast member (Jesse L. Martin) as series regulars, well, “The Flash” was as destined to break into song as Barry Allen was to become a superhero and repeatedly save Central City from villains.

The episode is also a Andrew Kreisberg Previews among various CW superhero shows: Melissa Benoist from “Supergirl,” John Barrowman from “Arrow,” and Victor Garber (“DC’s Legends of Tomorrow”) — all of whom have extensive musical theater experience — are just a few of the characters who will appear in “The Flash’s” tune-intensive episode, which airs Tuesday.

But the crossover begins in Monday’s “Supergirl,” explains Andrew Kreisberg, who is an executive producer on all of the CW’s superhero dramas.

“We set it up this way — that both Barry and Kara are at romantic crossroads with their respective love interests,” Kreisberg explains. As he notes, the big multi-show crossover event that occurred last fall was, while fun, largely cut off from each show’s ongoing narrative.

“It was its own thing, divorced from what was going on,” Kreisberg notes. “What I love so much about the musical is it really gives our characters an opportunity to address what they are going through. They’re going to address their romantic problems and [the experience will] help them get over it, because there’s nothing more romantic than a musical.”

Of course, they don’t engage in all the singing and dancing voluntarily. Darren Criss plays the Music Meister in Monday’s “Supergirl” and in Tuesday’s installment of “The Flash,” and he brings about the whole music-pocalypse. Not that the characters don’t enjoy it: Benj Pasek and Justin Paul, who were part of the “La La Land” music team, and the songwriters of “Crazy Ex-Girlfriend” — including co-creator Rachel Bloom — contributed songs to the episode, which also features classics like “Moon River.”

“We actually have a flashback in the beginning of the ‘Flash’ episode to Barry and his mother when he was a kid — they used to watch movie musicals together. She says, ‘Everything’s better in song,’” says Kreisberg, who shares story credit for the episode with executive producer Greg Berlanti (the teleplay is from co-executive producers Aaron Helbing and Todd Helbing)

The musical episode of “The Flash” — “Duet” — airs Tuesday at 8 p.m. ET/PT on the CW.

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