(L-R): Melissa Benoist and Grant Gustin Photo: The CW

The CW Extends "The Flash" Musical Crossover to one extra minute. Melissa Benoist, David Harewood and Chris Wood from "Supergirl" guest star in the March 21 episode. It all begins on Monday, March 20th with "Supergirl" episode entitled "Star-Crossed."

In "Star-Crossed," a new villain (guest star Teri Hatcher) comes to National City, putting Supergirl (Melissa Benoist) on high alert. Meanwhile, Winn’s (Jeremy Jordan) girlfriend, Lyra (guest star Tamzin Merchant), gets Winn in trouble with the law. Maggie (guest star Floriana Lima) attempts to help Winn but old loyalties get in the way. The Music Meister (Darren Criss) attacks Supergirl.

Teri Hatcher (Lois & Clark: The New Adventures of Superman), Kevin Sorbo and Darren Criss guest star.  

"The Flash" episode, which airs the following day will be extended one minute. The episode will end at 9:01 p.m., followed by "DC's Legends of Tomorrow" airing at 9:02 p.m.

Tuesday, March 21
"The Flash"
"Duet" - 8:00 p.m. ET/PT)
Darren Criss ("Glee') guest stars as the Music Meister in "The Flash" and "Supergirl" Musical Crossover. Barry (Grant Gustin) and the team are surprised when Mon-El (guest star Chris Wood) and Hank Henshaw (guest star David Harewood) arrive on their Earth carrying a comatose Supergirl (guest star Melissa Benoist) who was whammied by the Music Meister (guest star Darren Criss).

Unable to wake her up, they turn to Team Flash to save her. However, the Music Meister surprises The Flash and puts him in a similar coma, one that Team Flash can't cure. Kara and Barry wake up without their powers in an alternate reality where life is like a musical and the only way to escape is by following the script, complete with singing and dancing, to the end.