Grant Gustin as Barry, Melissa Benoist as Kara
“The Flash” star Grant Gustin said that the song “Super Friends,” co-penned by Rachel Bloom, was “very consistent” with the style of songs featured on “Crazy Ex-Girlfriend.” The CW

Tonight’s musical episode of “The Flash” features a wide variety of songs, but the most upbeat among all of them is probably the tune “Super Friends,” which “Crazy Ex-Girlfriend” star Rachel Bloom co-wrote for the TV special.

In an interview with Entertainment Weekly, Gustin described “Super Friends” and explained how it is different from other songs in the musical.

“We have a lot of different styles of songs. We have the standards. We have [Benj] Pasek and [Justin] Paul’s original song, and then Rachel’s. That one is more of a comedy piece and that’s the one we tap for. It’s fun,” Gustin said of “Super Friends,” which he said is “very consistent with that style of ‘Crazy Ex-Girlfriend.’”

READ: Which “The Magicians” actress landed a recurring role on “The Flash”?

Gustin revealed that Barry and Kara (Melissa Benoist) perform “Super Friends” as they start to embrace the fact that they are indeed trapped in a movie musical world.

“That’s the moment we’re really being engrossed in the musical and I think it’s the first time you see us kind of accept it,” Gustin said. “We’re trying to figure out the stages of the script to finish the play and get out essentially. So that’s the beginning of that process.”

“It’s a fun number. We have a good time,” the actor said of recording the song and filming the performance with Benoist. “That song’s kind of like a spoken singing song. There are pauses in it that we left empty when we recorded it to do whatever improv we could on the day. So there’s some fun looseness to that song, too.”

According to USA Today, Bloom made “Super Friends” with the help of her old “Robot Chicken” boss Tom Root in less than 24 hours. “That was a really nice exercise as a songwriter and flexing my muscles from doing a show with now 82 original songs and, OK, can I write a song this quickly,” Bloom said.

Despite Bloom and Root’s impressive songwriting skills, “The Flash” executive producer Andrew Kreisberg revealed to the New York Times that there were a few adjustments that were needed to be done in the song. Bloom had originally written a line where Barry sings, “And if I’m not there in time I’ll just go back in time and give it another shot.” So the show’s creators had to tell Bloom that the Flash’s time travel “actually ended up being a very bad decision.”

Watch the first few seconds of Barry and Kara’s performance of “Super Friends” in the sneak peek from Season 3, episode 17 below.

“The Flash” Season 3, episode 17, titled “Duet,” airs tonight at 8 p.m. EST on The CW.