This March's musical crossover between "Supergirl" and "The Flash" is going to be one big "Glee" reunion. TVLine reports that Darren Criss, who rose to fame as Blaine Anderson on "Glee," will appear as Music Meister in the two-episode crossover event.

“With our Flash and our Supergirl being 'Glee' alums, how could we not have them go up against another 'Glee' favorite like Darren Criss?” said executive producer Andrew Kreisberg. “We have been blown away by his talent over the years and we can’t wait to see what he brings to the Music Meister.”

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Criss will perform alongside “The Flash” stars Grant Gustin, Jesse L. Martin and Carlos Valdes; “Supergirl” stars Melissa Benoist and Jeremy Jordan; and “Legends of Tomorrow” co-star Victor Garber and “Arrow” regular John Barrowman. Titled "Duet," the musical also stars “Supergirl” actors David Harewood and Chris Wood and is directed by Arrowverse veteran Dermott Downs.

Notably, Gustin and Benoist also appeared on "Glee." In fact, Gustin's Sebastian was introduced as a student at the Dalton Academy, where Criss' character Blaine went to school; a fellow member of the Dalton Academy Warblers, Sebastian was introduced as a romantic rival for main character Kurt (Chris Colfer), who would go on to fall in love with Blaine.

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Prior to "Glee," Criss' claim to fame was his role as Harry Potter in StarKid's musical production of "A Very Potter Musical." He went on to star on Broadway in the revival of "How to Succeed in Business Without Really Trying," taking over for "Harry Potter" star Daniel Radcliffe. His past stage work also includes "Hedwig and the Angry Inch," "A Christmas Carol" and "A Midsummer Night's Dream."

The musical episode will take place on the March 21 edition of “The Flash,” with a lead-in on the March 20 episode of “Supergirl,” similar to how last fall’s four-show crossover between The CW’s DC Comics-based shows kicked off with a short lead-in scene on “Supergirl.” This falls roughly a year after the first TV meeting between “The Flash” and “Supergirl,” which happened on the “Worlds Finest” episode of “Supergirl” in March 2016.

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“The Flash” returns on January 24. 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.

Starring Melissa Benoist as the Girl of Steel, “Supergirl” airs Mondays at 8 pm ET/PT on The CW. The series also stars David Harewood as Martian Manhunter, Mehcad Brooks as Jimmy Olsen, Chyler Leigh as Alex Danvers and Jeremy Jordan as Winn Schott and features appearances by Calista Flockhart’s Cat Grant as well as Tyler Hoechlin’s Superman.