The highly anticipated Flash and Supergirl musical crossover is almost here! And after some incredibly dark times on both CW-DC series, the stars promise there's some lighthearted fun to be had when Kara (Melissa Benoist) and Barry (Grant Gustin) find themselves trapped in a dangerous dreamworld by the charismatic Music Meister (Darren Criss).

"It was just ... for the actors and the crew, a fun escape from how dark it's been all season," Gustin told at PaleyFest this past weekend. "We kind of go into this world of escapism where we're having fun and singing and dancing. We're even in a new era. Everyone got to wear different kind of clothes and have their hair different."

Adds executive producer Todd Helbing: "I think sometimes our cast is at the best, and our show is at the best, when it's more lighthearted episodes."

The Flash and Supergirl musical crossover episode "Duet" airs Tuesday at 8/7c on The CW.

(Full disclosure: is owned by CBS, which is one of The CW's parent companies.)