Tom Cavanagh as Dr. Harrison Wells
Tom Cavanagh revealed his reaction when he found out that they're doing a musical crossover between “The Flash” and “Supergirl” this TV season. The CW

Tom Cavanagh was a little bit surprised when he learned that they is going to be a musical crossover between “The Flash” and “Supergirl” this TV season.

“Isn’t this the domain of Season 7, grasping at straws?” Cavanagh told Variety when asked what his reaction was when he found out about the crossover. “We’re in season three! We seem to be doing just fine. Why do you want to jeopardize this by having people opening their mouths in song?”

The 52-year-old actor, on the other hand, understands that they’re doing it for the fans. “I would call that respect for the comic-book world, for the people who are keeping our show alive, for the fans,” Cavanagh said. “It’s like, ‘Look, we’re not sitting back and repeating the pilot,’ so I guess you can make the argument that having a singing episode is just one more version of us moving things along and moving forward.”

“I think it’s a sign of respect that we’re willing to attempt it,” added the “Ed” alum, who portrays various versions of Dr. Harrison Wells on the CW series. “Also we have no choice.”

Even though it appears that Cavanagh doesn’t know much about the plot details of the musical, he has an idea on how the crossover would be a success.

“I would say the lynchpin to the success of the musical episode for us is to go through Carlos Valdes. He is incredible,” the Canadian actor said of his “The Flash” fellow cast member, who plays Cisco Ramon.

In an interview with Entertainment Tonight, Cavanagh’s co-star Candice Patton said that she and the rest of the cast “are all kind of just waiting for more details” about the musical. But Greg Berlanti — who serves as an executive producer on both “The Flash” and “Supergirl” — previously revealed that the episode is going to feature some original songs.

“We’ll have to start talking about clearing music,” Berlanti told IndieWire last month. “I have a few ideas for tone and style in my head but we’re just starting to talk about what that can be. I do want to try and get an original piece of music written. As we make a deal on that we’ll probably make some announcements on the original songs.”

Although the villain in the musical has not been announced yet, executive producer Andrew Kreisberg said in an interview with Collider in August that the baddie of the episode “can make you think your friends are singing and dancing in front of you.”

The musical crossover is set to air sometime in spring 2017. “The Flash” Season 3 airs every Tuesday at 8 p.m. ET on The CW, while “Supergirl” Season 2 premieres on Monday, Oct. 10, on the same network.