Viewers were first teased with the villainous ape in the Pilot, where a torn cage was shown displaying a 'Grodd' nametag. Then in "Plastique," during the final moments of the episode, it was revealed through a flashback that General Eiling was conducting inhumane tests on a gorilla. This resulted in Eiling and Wells parting ways.
Since then, Grodd has not been mentioned on the show but behind the scenes, a lot has been revealed.
[The Flash](series:1068303) stunt coordinator, Jon Krait, revealed via Twitter that a man named Simon Burnett was Grodd. Burnett is a stuntman that appeared in a variety of films, including, Rise of the Planet of the Apes. It appeared that the producers of The Flash were planning to use practical effects to bring Grodd to life.
But it was revealed by executive producer, Andrew Kreisberg that they have seen test footage of how Grodd will appear on the show.
It appears that Grodd will make an appearance thanks to a combination of visual effects and prosthetics. Producers have already said that Grodd will appear this seasons, which means that Grodd will appear at some point towards the end of the season.
The Flash airs Tuesdays at 8pm on The CW.