Gustin responded that he always enjoyed it when they could incorporate some music into The Flash, most notably in the karaoke scene from a few episodes ago.
He surprised some people, though, by answering a question many members of the cast get pretty regularly, even without it being explicitly asked.
"I don't want to do a musical episode," Gustin said. "But it's fun getting some singing in when we can."
Since the series started, Gustin -- flanked by musical actors like Andy Mientus, Jesse L. Martin, Victor Garber and others, plus executive producers Andrew Kreisberg and Marc Guggenheim, both of whom worked (with Garber) on the musical TV series Eli Stone, fans have asked that question.
Here are some of the responses we've heard over time:
Jesse L. Martin
"You know what, yeah? Why wouldn't I?" Martin told ComicBook.com at New York Comic Con last year, just days after the series' launch. "Of course, I'd have a blast with it. We joked about i for a long time. WE'd make up jokes on set about what it could possibly be if The Flash did a musical episode and we all just thought it was funny and a lark. But the more it gets talked about, I think the more seriously Greg [Berlanti] and Andrew [Kreisberg] take it. And they've been prodded in many ways by many different people: Why don't you guys do something? You've got all these actors who can do it so you guys should probably think about doing it. So -- you never know, it might happen."
He added, "I don't know how they'd do it, but they certainly have the resources if they want to do it. I mean, you've got all of these super-talented people on the set. So if they wanted to do it, we could really knock out a great musical episode."
"Maybe not on-camera but I guarantee you that if you come to our set anytime the three of us are there," Cavanagh said when ComicBook.com's Emily Donn asked whether a musical episode was coming. "We do a lot of singing on set, a lot of dancing. It's true -- it'll be like, 'Can you guys stop tap dancing so we can shoot the scene?'"
Added producer Andrew Kreisberg, "One of the big differences between Arrow and Flash is that on Flash, people go out for drinks at the end of the day. They're all friends and they all care about each other so there has been some talk about ending an episode with everybody getting in a karaoke bar."
"I don't know is the answer to that, and I'm not sure it would really work," admitted Garber, who is now expected to carry his role from The Flash over to a new spinoff featuring Firestorm, The Atom, Canary and more. "I think that Eli Stone was really one of the first of those shows and God knows there's been a few since. I think Grant sang on [a previous] episode of The Flash, didn't he? At a karaoke bar? I think that's about as close...I don't think they're going to get Martin Stein up at a karaoke bar. I don't know how they're going to get him to sing, so I wouldn't hold my breath if I were you."