It has become an annual tradition on The Flash to find a musical number or two mixed into an episode. In season 1, Barry Allen (Grant Gustin, ex-Glee) and Caitlin Snow (Danielle Panabaker) spent some time at a karaoke club. Last season, while undercover on Earth-2 as his counterpart, Barry encounters that world's Joe West (Jesse L. Martin, ex-Law & Order) doing some crooning.
Tonight sees Glee alumnus Darren Criss bring to life a villain from Batman: The Brave & The Bold, the Music Meister. While some folks were wishing that Neil Patrick Harris, who originated the role in the cartoon, could've been brought in for the shot, it was decided to have Criss come in for a 1-shot mini-Glee reunion with Gustin and Supergirl star Melissa Benoist. The Music Meister's machinations began last night at the end of Supergirl, but while you're waiting, let's go back a year for last year's musical interlude, with "Where or When" & "My Funny Valentine".
One local paper teased that Carlos Valdes (Cisco) would also be singing in this episode. We shall see.