The Flash is taking a trip down memory lane for its 100th episode. Directed by cast member Tom Cavanagh, "What's Past is Prologue" finds Barry Allen (Grant Gustin) traveling back in time to collect items and artifacts the team requires to assemble a weapon that will defeat Cicada (Chris Klein) in the present day. Along the way, viewers can also expect some touching moments, bombshells and cameos by various longstanding rogues.
At a red carpet event in Vancouver, The Flash actors weighed in on the series' milestone, Cavanagh stepping behind the camera, and the return of Eobard Thawne.
"I was excited by the script," Gustin told SYFY WIRE. "I knew Tom Cavanagh was directing. He's probably my favorite director to work with because he's one of my best friends. We had a great time. We did time-travel moments that we've never done before. We got to see a lot of big bads from the past, Eobard Thawne being one, which is one of my favorite dynamics that we've ever had on the show."
Candice Patton, who plays Iris, echoed those sentiments. "I love that we visit old memories of The Flash in new and different ways," she says. "Also, having Tom Cavanagh direct it was a really honorable nod to these last 100 episodes. Since day one, he's been a father figure of the show along with Jesse Martin. It's so great that he's directing such a monumental episode. That, for me, was important having him there."
Accompanying Barry on this quest is his future daughter, Nora (Jessica Parker Kennedy). The speedster gets to witness some personal interaction between her parents. As a result, Gustin says, "It brings them a lot closer together."
"It allows Nora to see Barry's journey through a different lens and understand what they've been through," he says. "It's different than just going through a museum and reading the things that the Flash did. Barry gains more trust of Nora."
Parker Kennedy gushed over Nora's heavy involvement in the episode.
"I was very surprised to have been a part of the celebration," she says. "I really thought it would be the main characters doing everything. When I read the script, I was just floored and humbled and excited to be a part of the whole thing. It's nice because I wasn't in the past seasons. It's a way for me to be incorporated, so it's really special."
"What's Past is Prologue" plays like The Flash's greatest hits. It features cameos by plenty of former foes. There's Nora's perspective on previous proceedings that have already transpired. However, time travel rules, not to mention paradoxes, can give the most avid Flash fan a headache. There's a lot going on. Even actor Hartley Sawyer, who joined The Flash as stretching sleuth Ralph Dibny last year, needed to wrap his head around the story's details.
"I had to read the script two or three times before I really got it," Sawyer says. "I was like, 'Wait. What year are we in?' I thought it was really fun for Ralph because, in the final cut, he got to look at it and go, 'What does this mean? Who is that? Ok. No, I don't got it.' I love that because if you are an audience member and you haven't watched since day one and you are jumping in, you are going to have the same questions Ralph has. I love that he does that stuff. It's kind of a nudge to the audience like, 'We know we've done 100 of these. We know we've done so many. Let's see what that means and how it's going to play out.'"
The episode doesn't forget Cicada (Chris Klein), either. Eventually, the team confronts him on their own terms. How that goes down remains to be seen. However, Killer Frost (Danielle Panabaker) becomes instrumental in the battle. Panabaker was thrilled to have Caitlin's icy alter-ego back in action, especially considering that personality has been dormant for most of this season.
"I've missed her," Panabaker says. "Obviously, I can't keep up with all Tom Cavanagh's multiple characters, but the ability to play two such different characters on the same show is incredible. I'm really excited about this season. I think they've done an amazing job about giving me great stuff to do."