Ever since The CW began growing its DC Comics television universe - introducing Barry Allen (Grant Gustin) on Arrow then giving him a spinoff in The Flash - the network has featured crossovers between its series. The Arrow and The Flash crossover in late 2015 worked to set up Legends of Tomorrow, then last year's mega-crossover introduced Kara Danvers (Melissa Benoist) to the majority of the Earth-1 heroes after Supergirl moved to The CW from CBS following its first season. But, while The CW already had its big crossover for this season with the three-night 'Invasion!' storyline, another team-up is still headed our way.

In two weeks time Barry and Kara are set to join forces for The Flash and Supergirl musical crossover in which they'll battle the DC Comics villain Music Meister, portrayed by Darren Criss - a Glee alum who appeared on Fox's musical dramedy alongside both Gustin and Benoist. Although The CW debuted the first promo for the musical crossover last night, it didn't include a look at Music Meister. Now, the first image from the team-up episode features Music Meister and another Arrowverse character set to appear.

EW released a new image from The Flash's March 21st episode, titled 'Duet', in which the majority of the crossover storyline will take place - after a brief set up in Supergirl's March 20th episode, 'Star-Crossed', similar to the show's lead-in to the 'Invasion!' storyline. Additionally, ComicBook.com, TV Guide Magazine, Mashable, and E! News debuted photos from the episode. Take a look in the gallery below.

[vn_gallery name="Supergirl/Flash Musical Episode Images" id="918314"]

Featured in many of the images are Benoist and Gustin, whose characters will perform a duet on the original song "Superfriends" written by Rachel Bloom, creator/star of The CW's Crazy Ex-Girlfriend. 'Duet' features a second original composition penned by La La Land duo Benj Pasek and Justin Paul titled "Runnin' Home to You" that will be sung by Gustin. Additionally confirmed to sing in 'Duet' are Arrowverse characters Joe West (Jesse L. Martin), Cisco Ramon aka Vibe (Carlos Valdes), Winn Schott (Jeremy Jordan) Professor Martin Stein (Victor Garber), and Malcolm Merlyn (John Barrowman). Supergirl's Mon-El (Chris Wood) and J'onn J'onzz aka Martian Manhunter (David Harewood) will also appear in 'Duet', but without singing parts.

As revealed in the synopsis for The Flash's 'Duet', the episode will see both Kara and Barry "whammied" by Music Meister, leaving them outwardly comatose but stuck in an alternate reality where they'll need to follow the villain's script in order to escape. As evidenced by these photos from 'Duet' and the promo for the episode, the alternate reality will have a distinct vintage feel to it - first teased in 1940s-set images from The Flash. Previous set photos additionally introduced Criss as Music Meister, though not within the alternate reality - instead, he faced off against Vibe, Martian Manhunter, and Wally West aka Kid Flash (Keiynan Lonsdale).

Of course, while these images from 'Duet' show off the dancing fans can expect from Barry and Kara in the musical crossover - and officially introduce Music Meister - it remains to be seen, or rather heard, how the music for the episode will come together. Both Bloom and the team of Pasek and Paul are accomplished songwriters, and fans are likely looking forward to hearing their contributions to The Flash and Supergirl crossover. But, we may not get a chance to hear either of the original songs, or any other musical numbers from the episode, until closer to its premiere date.

Next: Flash/Supergirl Musical Crossover Promo

Supergirl continues Monday, March 20 with ‘Star-Crossed’ at 8pm on The CW. The Flash Tuesday March 7 with ‘The Wrath of Savitar’ at 8pm on The CW.

Source: EW, ComicBook.com, TV Guide Magazine, Mashable, E! News