The Flash-Supergirl musical crossover villain revealed

Ever since it was announced that The Flash and Supergirl would be crossing over for a musical episode, fans have been eagerly awaiting to find out the reason why. Which villain could make the heroes of Central City and National City break into song?! Now, we have our answer:

“It is going to be the Music Meister,” executive producer Greg Berlanti told reporters while promoting his upcoming drama Riverdale at the Television Critics Association’s press tour on Sunday. “We’re finishing writing the script this weekend.”

A villain with the power to control people through song, The Music Meister was famously brought to life in the animated series Batman: The Brave and the Bold. In the episode “Mayhem of the Music Meister,” Neil Patrick Harris voiced the villain. Could he reprise that role in real life for the crossover? “We haven’t gone about casting it yet,” Berlanti says. “But it’s the right question, though.”

Practically the entire cast of The Flash has musical talents, including Grant Gustin and Jesse L. Martin, as well as the Supergirl cast, including Melissa Benoist and Jeremy Jordan. “There are going to be people from both shows singing,” executive producer Andrew Kreisberg says, noting that the musical crossover will start on Supergirl and resolve on The Flash.

“When we get to the musical episode, both Barry and Kara will find themselves at pivotal crossroads on their respective series,” Kreisberg says. “The experience of going through the musical will have a great impact on both series moving forward.”

In terms of the music, it’s unclear whether it will be original songs or covers. “We’re still working that out right now,” Kreisberg says. “We’re still writing the script and trying to figure out exactly what we’re going to do.”

Supergirl returns Monday, Jan. 23 at 8 p.m. ET, while The Flash returns Tuesday, Jan. 24 at 8 p.m. ET on The CW.