"This is the favourite character I've played so far in my young career. So I'm having the time of my life. I mean, he's just so endearing. He's so sweet. He's curious. He's a nerd, yeah. And now he's a superhero. There aren't that many better characters out there."
This The Flash marks itself apart from the fondly recalled 1990 live-action TV show by embracing, rather than running from, the character's deep comic-book mythology. It connects to the earlier series, however, by casting John Wesley Shipp (the 1990 Barry Allen) as the father of the main character in this show.
"All of us are huge fans of the original Flash," says executive producer Andrew Kreisberg.
"That show ended far too soon as far as we were concerned. And Greg [Berlanti, fellow executive producer] had worked with John on Dawson's Creek - he played Dawson's father.
"So when we were sitting down and talking about developing this series, all three of us were like, 'Whatever we do, we've got to get John Wesley Shipp.' I think he was sort of surprised that the show had meant as much to us and to a lot of people as it did, because
I think it ended far too soon for him as well.
"So [it was great] to get to have that link to the past and be able to have him be part of the show, and it's not just a gimmick, either. It's not a cameo. He's playing one of the most important parts on the show.
"So much of what Barry is doing, he's doing for his father."
As the first episode demonstrated, that father/son relationship is key to this version of The Flash. "Well, he's always wanted to help people," says Gustin of his character.
"I mean, his life goal is always to make up for what put his dad in prison and get him out and help his dad in any way he can. Now he has these powers and he can use them to help other people's families so nobody has to experience what Barry experienced when he was 11."
The 11-year-old Gustin, however, presaged his future as the Fastest Man Alive.
"I actually was very fast as a kid but, ironically, I hated running.
"And I quit soccer because I thought it was ridiculous that we were running back and forth."