When Supergirl arrives on "The Flash" in a few short weeks, both she and Barry will be trapped inside a musical dreamland, thanks to the villainous Music Meister. According to this new synopsis, the pair will have to sing and dance their way back to reality.
The first part of the musical crossover will take place on March 20, in the "Supergirl" episode titled "Star-Crossed." The musical will continue on "The Flash" during "Duet," which will air on March 21:
DARREN CRISS (“GLEE”) GUEST STARS AS THE MUSIC MEISTER IN THE FLASH AND SUPERGIRL MUSICAL CROSSOVER – Barry (Grant Gustin) and team are surprised when Mon-El (guest star Chris Wood) and Hank Henshaw (guest star David Harewood) arrive on their Earth carrying a comatose Supergirl (guest star Melissa Benoist) who was whammied by the Music Meister (guest star Darren Criss). Unable to wake her up, they turn to Team Flash to save her. However, the Music Meister surprises The Flash and puts him in a similar coma, one that Team Flash can’t cure. Kara and Barry wake up without their powers in an alternate reality where life is like a musical and the only way to escape is by following the script, complete with singing and dancing, to the end. Dermott Downs directed the episode with story by Greg Berlanti & Andrew Kreisberg and teleplay by Aaron Helbing & Todd Helbing. Original airdate 3/21/2017.
This episode will mark a reunion between Darren Criss, Grant Gustin, and Melissa Benoist, who all previously starred together on "Glee." The episode will feature a mix of original songs written by "Crazy Ex-Girlfriend" star Rachel Bloom and Academy Award-winning "La La Land" songwriters Benj Pasek and Justin Paul. The musical will also feature a variety of cover songs and will be set in the 1940s.
Starring Grant Gustin as the Scarlet Speedster, “The Flash” airs Tuesdays at 8 pm ET/PT on The CW. The series also stars Jesse L. Martin, Tom Cavanagh, Carlos Valdes, Candice Patton, Danielle Panabaker, Keiynan Lonsdale and more.