The Flash and Supergirl musical crossover will double as a Glee reunion. Darren Criss will guest-star as the villain Music Meister, reuniting with his former Glee co-stars Melissa Benoist and Grant Gustin, TVLine reports.

"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."

Music Meister is a character that originated in the animated series Batman: The Brave and the Bold. A formerly bullied child, Music Meister hypnotizes people with his singing to force them to do his bidding.

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Criss starred on Glee for five seasons as Blaine Anderson, during which time Gustin briefly played his love interest. His other credits include a guest stint on American Horror Story: Hotel and headlining the Broadway version of Hedwig and the Angry Inch.

The anticipated two-part crossover will begin during on Supergirl on Monday, March 20 (8/7c) and conclude on The Flash on Tuesday, March 21 (8/7c). The cast members set to sing include The Flash's Gustin, Carlos Valdes and JesseL. Martin; Supergirl's Benoist and Jeremy Jordan; Legends of Tomorrow's Victor Garber and John Barrowman; and, of course, Criss.

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