We’re just one week away from Barry and Kara singing their super-hearts out when The Flash and Supergirl meet for a musical “Duet,” but why wait? Ahead of a full trailer, DC goes behind the scenes with a new all-access featurette teasing Darren Criss’ Music Meister, familiar faces and a show-stopping number.

Even as “Duet” isn’t about to give up its original songs just yet, a new DC All-Access featurette offers a fairly in-depth look at the crossover episode, particularly its choreography and construction with Darren Criss at the helm. Iris too gets a chance to shine as a new fantasy character, while Victor Garber and Jesse L. Martin gush about getting to sing with one another (the Flash portion starts around 1:56).

The March 21 event (technically kicking off March 20) will feature original musical numbers like the Rachel Bloom-written “Super Friend,” and La La Land duo Benj Pasek and Justin Paul’s “Runnin’ Home to You.” Other tracks include a Melissa Benoist cover of “Moon River,” an ensemble performance of Jackie DeShannon’s “Put a Little Love in Your Heart,” and an upbeat dance number choreographed by Glee’s Zachary Woodlee.

Here’s the “Duet” synopsis, which explains the full musical premise:

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.

The two-night event will get started with Supergirl on March 20, and crescendo in the following night’s Flash “Duet.” You can check out the first photos and footage below, and stay tuned for more.

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