Although first launched in 2012 with Arrow, The CW's shared DC Comics television universe has grown to include the likes of The Flash, Legends of Tomorrow, and CBS transplant Supergirl. When the solo show following Kara Danvers (Melissa Benoist) was first being developed, fans wondered whether it would crossover with any of The CW's series. That ended up happening in Supergirl season 1 when Barry Allen (Grant Gustin) traveled to National City by way of the multiverse - The Flash takes place on Earth-1 while Supergirl lives on Earth-38. Then, they met up again after the series moved to The CW when Kara joined the network's lineup of heroes for the 'Invasion!' event.
Now, Kara and Barry are set to team up once again in the Supergirl and The Flash musical crossover that will kick off in the former's March 20th episode, 'Star-Crossed', and take place mainly in the latter's March 21st episode, 'Duet'. The synopsis for The Flash's 'Duet' revealed the two heroes will be "whammied" by DC Comics villain Music Meister, played by Glee alum Darren Criss, and trapped in an alternate reality in which Kara and Barry will need to play through the villain's script in order to escape. Now, the stars and producers of The Flash and Supergirl discuss the episode and the potential of a followup.
EW interviewed the stars of The Flash and Supergirl on the set of 'Duet' including Benoist, Gustin, Criss, and fellow featured performers in the crossover Carlos Valdes (Cisco Ramon aka Vibe), Jeremy Jordan (Winn Schott), and John Barrowman (Malcolm Merlyn). In fact, Arrowverse producer Andrew Kreisberg revealed discussions of a musical crossover have taken place since the beginning: "We’ve always talked about doing it, from the very beginning, more in a joking way." Meanwhile, Gustin was more skeptical, "I didn’t ever think it would be a real thing, so when they told me it was real, I was like, 'How?!'"
As EW reports, Music Meister's alternate reality in 'Duet' was inspired by The Wizard of Oz in that characters from The Flash and Supergirl will play different roles in the 1940s-inspired "movie." Barrowman, Victor Garber (Professor Martin Stein), and Jesse L. Martin (Joe West) will portray rival mob bosses, while Jordan will be a club pianist and Valdes an "aspiring artist busboy." The episode will include covers of classic songs like Jackie DeShannon's "Put a Little Love in Your Heart" - a group number that includes Barrowman and Gustin tap dancing - and Andy Williams' "Moon River," sung solo by Benoist.
In addition to the covers, 'Duet' will feature two original songs. One is "Superfriends," co-written by Rachel Bloom, creator/star of The CW's Crazy Ex-Girlfriend, that's sung by Supergirl and The Flash - which Gustin says is a "goofy song [that's] very consistent with that style." The other is "Runnin' Home to You" written by La La Land duo Benj Pasek and Justin Paul that will be sung by Gustin. Although we've yet to hear any of the music from crossover episode, The Flash 'Duet' promo did offer us a glimpse at the '40s-set alternate reality.
Of course, it remains to be seen how successful the musical crossover proves to be, both in terms of garnering ratings for The CW - the 'Invasion!' event did provide the network with its highest numbers in six years - and critical/fan response. Still Kreisberg is reportedly hopeful for a sequel at some point down the line, while Criss additionally wants to return as Music Meister: “I want to come back, I’m not done — then I’ll have my true payback!” Still, real discussions of a potential followup musical crossover will likely wait until after The Flash and Supergirl meet again in 'Duet.'
Supergirl continues Monday, March 20 with ‘Star-Crossed’ at 8pm on The CW. The Flash Tuesday, March 14 with ‘Into the Speed Force’ at 8pm on The CW.