Tom Cavanagh on the Challenges and Privilege of Directing 'The Flash' #100

Tom Cavanagh, who plays Harrison Wells, Eobard Thawne (sometimes), and various other multiversal [...]

Tom Cavanagh, who plays Harrison Wells, Eobard Thawne (sometimes), and various other multiversal doppelgangers of both on The CW's The Flash, stepped behind the camera to film the show's hundredth episode, "What's Past is Prologue," which aired tonight.

During a reception for the episode, Cavanagh shrugged off a question from about the most challenging aspects of filming the landmark episode, which saw Barry Allen and his daughter Nora traveling back through the show's history to collect items they could use to defeat Cicada. A combination of inserting the actors into existing shots, bringing back old guest stars, and creating wholly new elements was used to create an episode that plays with the nature of reality and the complications of time travel.

"It was so enjoyable," Cavanagh said. "First off, when they asked, I was like 'Oh, yeah, I'd love to. It'd be amazing.' And then you just don't want to muck it up for everybody. You know, there's a lot of people here who know the show very, very well, and one of the dangers when you're directing the 100th is to not just do simple nods to the stuff we've done int he past and done well. It's a simple way of doing it: you're like, 'hey, we did this, and wasn't that great?' And the viewers are like, 'yeah, that was fun.' But it doesn't really hold water as a story for right now, right here. So the largest challenge is what can we do? So it's like if they have to go back and get things to defeat the main villain, or one of the main villains, of the season, that's going to be an organic way of doing it. For me as a director, you're trying to combine things you have seen with a fresh way of doing it. I loved doing it. I loved working with Jessica Parker Kennedy and Grant Gustin, who really had to carry that trip back to the Flash to fix the future. Also playing my one of my favorite characters I've ever played, or a few variations on that character, was a real treat."

Fans will get more from Cavanagh this season, as the actor hinted that his latest iteration of Wells -- the French detective Sherloque Wells -- is going to continue to be a thorn in Nora's side.

The Flash airs on Tuesday nights at 8 p.m. ET/PT, before episodes of Black Lightning on The CW.