Though “The Flash” star Grant Gustin has been privy to Jessica Parker Kennedy’s secret role since the beginning of Season 4 of the CW series, the mystery surrounding the yet-to-be-named character still keeps the show’s lead actor at the edge of his seat.

“I’ve known since before we started this season,” Gustin told Entertainment Weekly of the mystery girl’s identity. “It’s been the thing that I’ve been most excited about all season, which sounds ridiculous because it’s really a Season 5 thing. I’ve spent all of Season 4 being excited about this thing that we’re going to do in Season 5!”

Kennedy’s character made her debut in last year’s Arrowverse crossover event “Crisis on Earth-X,” in which she appeared as an overly excited waitress at Barry (Grant Gustin) and Iris’ (Candice Patton) wedding. Though the mysterious character was perky during most of her cameos, her mood suddenly turned somber after Caitlin (Danielle Panabaker) and Harry (Tom Cavanagh) bumped into her at CC Jitters in Season 4, episode 15.

“I will actually say, I know who she is and a little bit about her backstory, and how she’s connected to a handful of characters,” Gustin shared. “But I didn’t know what that was when I watched that episode. I was like, ‘Huh, I wonder what that’s about.’”

The mystery girl’s appearance in episode 15 also left Panabaker intrigued. “That, to me, is actually the fun of watching our show sometimes, because what I read on the page is not necessarily the way things end up cut together,” Panabaker said. “Harry and Caitlin leave the scene and then there’s the push-in on the mystery girl, and when I watched the show I was like, ‘Oh, that’s a very different look than she gave me the rest of the scene. What does it mean?!’”

As first revealed by TV Guide last month, fans have to wait until the Season 4 finale to find out the identity of Kennedy’s character. It was later confirmed by executive producer Todd Helbing, who told Entertainment Weekly that “there’s actually an extra little bonus [in the finale] where something happens where you’ll realize exactly how she’ll play a part in the future.”

Are you excited to find out who the mystery girl really is? Tell us in the comments section below!

“The Flash” Season 4 finale, titled “We Are the Flash,” airs on Tuesday, May 22 at 8 p.m. EDT on The CW.

Jessica Parker Kennedy as mystery girl on ‘The Flash’
“The Flash” star Grant Gustin said that the mystery surrounding Jessica Parker Kennedy’s character is the thing he has been most excited about all season. The CW