'Supergirl' and 'The Flash' double up for musical crossover

"Supergirl" star Melissa Benoist and Grant Gustin of "The Flash" will feature in back-to-back crossover episodes which see the superheroes meet up in a most musical manner.

"When they're not acting or flying or punching or exploding things, they're singing," promised Ali Adler, who is an executive producer on "Supergirl."

Adler had worked with both Benoist and Gustin on high school musical comedy drama "Glee" before she came to The CW series -- which moved over from CBS after its first season.

Speaking during an event on The CW's Television Critics Association summer tour, Greg Berlanti, an executive producer on both "Supergirl" and "The Flash," reminded attendees of his "personal love for musicals," as Variety noted, acknowledging that "we have a number of people who can sing across all the shows."

So when will this unusually musical pair of episodes arrive?

Both "The Flash" and "Supergirl" return in October, and TV Line had Berlanti forseeing a double header "in the back half of the year."

The majority of the repertoire will comprise pre-existing songs, Berlanti said, though revealed that the show's writers were keen to get in on the action too, aiming for "at least one original song per episode."

There was also news about two new characters coming to "Supergirl" for its second season.

Chris Wood of "The Vampire Diaries" and "Containment" will play Mon-El, someone with superpowers similar to Supergirl's, who, while not from Krypton, escaped her home planet before it was destroyed.