One of the best things about The Flash’s first season was that it took on the challenge of Gorilla Grodd, a giant, talking, psychic gorilla. That would be a challenge on a movie budget, with a movie’s post-production time. The Flash did it for TV.

In the case of Grodd, the show started working on him from the pilot on. In an earlier interview, visual effects supervisor Armen Kevorkian told The Hollywood Reporter that they started working on a CG model right after they completed the pilot:

After we completed the pilot, Greg, Andrew and Geoff Johns gave me a heads up that they wanted to introduce Grodd this season. It allowed me on the side with my guys to think about how we would do this character. It does give you a little more time, even the thinking part of how we would organize things to get to where we want to when the time came. We just started building him a little bit in advance. But you are involved with episodes that actually air, so there’s only so much time you have to spend on side projects.

For the fight, he then explained, the subway tunnel was a real set, but Grodd was entirely computer-generated. They also drew a lot of inspiration from the comic:

We referenced both the comic book — for his size and personality — and footage of gorillas to ground it in reality. Grodd’s around 8 feet tall and about 800 pounds. He also has telepathic powers, so facial expressions were really important to get across what he was trying to convey.

The facial expressions were really important, since Grodd (smartly, in my opinion) only spoke mind-to-mind, not out loud. Frankly, that might have been a little hard to watch without laughing.
The Hollywood Reporter has a run-down of three major special effects from three shows: a splinter-y death on Agents of SHIELD, the Flash-Grodd fight from The Flash, and a Dragon attack from Game of Thrones.

Source: io9 How The Flash Effects Team Used Comics to Bring Gorilla Grodd to Life  |  Contact the author at katharine@io9.com.