Series 3, Episode 13
Attack on Gorilla City
I don't much like Grodd episodes, and I think I've finally started to pin down a few reasons why. Firstly, I'm not very keen on talking animals in things which aren't about talking animals -- they add a layer of narm that is often difficult to shake. But secondly, The Flash does such a horrendously poor job of selling the fact that Grodd is actually a real, live character who's physically present in scenes with other characters.