Last week, Barry (Grant Gustin), Cisco (Carlos Valdes), Caitlin (Danielle Panabaker), and Julian (Tom Felton) headed to Earth-2 on a mission to save Harry Wells (Tom Cavanagh) from Gorilla City. Now the fight is coming to them.

Along with saving Wells from Gorilla City, Barry had hoped he could change another news headline — the one mentioning Central City recovering from a gorilla attack — he saw from the future where Savitar kills Iris (Candice Patton). However, in taking down Solovar, the gorilla’s leader, his old enemy Grodd was put into power with a singular goal of returning to Earth-1 Central City and wreaking havoc.

Variety spoke with executive producer Aaron Helbing about Grodd’s army coming to town, and how the city — and the Flash — handles it.

Grodd got his introduction in Season 1; in Season 2 you brought him back, and surprised a lot of people by introducing King Shark. Now you’re doing this mini-event with an army of gorillas. Have these episodes with big CG characters become easier? Have you grown more confident in making them?

I wouldn’t say they become easier. I think every episode has its own unique challenge, but we always strive to swing for the fences. When you have a team like Encore — who does our visual effects — honestly anything is possible. You see what they did last week with the arena fight against Solovar, and what they did with King Shark last season, and it gives us confidence.

Changing the future is a pretty complicated process. Last week he thought stopping Solovar would stop the gorilla army from coming to Earth-1, but it actually put Grodd into power so they could attack the city. Is Barry starting to worry that him trying to change the future is what leads to what he saw there happening?

Barry is mindful of it, but at the same time — because the woman he loves life’s hangs in the the balance — he’s going to do whatever he can to save her. Whether it was Solovar or Grodd, he knew gorillas attacked Central City and for him that was enough to try and change the future.

Grodd has amassed quite the army to bring to Central City — which has seen its fair share of unusual things. I’m curious how the city itself reacts.

It’s definitely a new level of insanity. The thing about the city, though, is they have the Flash, they have Kid Flash (Keiynan Lonsdale), they have Jesse Quick (Violett Beane). They always sort of feel that, whatever comes their way, the Flash will save the day.

Will he be working at all with the CCPD against Grodd, or is it basically speedsters vs. gorillas?

The CCPD is definitely involved. You’ll see Joe (Jesse L. Martin) involved as a cop and they’re doing whatever they can to stop the gorillas from overrunning the city.

At the end of last week’s episode we saw Gypsy (Jessica Camacho) working with Grodd. Is she being forced to work with him?

Gypsy has feelings for Cisco, so I don’t think she’d want anything to happen to him. When we first see her this week, she tries to take on the team, but the team realizes she’s under Grodd’s control, which tips them off that he’s no longer on Earth-2.

Jesse mentioned staying on Earth-1 to be with Wally. Is she committed to that choice or is she still on the fence?

She’s committed to Wally, but she also has a father. She would like to get his blessing, especially after everything he did for her last season. She wants to make sure he’s okay with it, but Harry Wells being who he is, he’s not going to let her off the hook that easily.

The interaction between Harry and H.R. last week was great. How do they get along as they spend more time together?

There will definitely be some headbutting. This is Harry’s first encounter with H.R. for an extended period of time, and the two quickly realize how different they are even though they share the same face.

There were some promo images released last week and one of them included the Accelerated Man from Earth-19. Can you tease what his role in the episode is?

He’s more of just an Easter Egg to be honest. As of now, this will be the only time we see Accelerated Man.