The Mutation Situation - S2-E1
Trivia: At the very end of the episode, a squirrel drinks some mutigen and then suddenly looks back at the camera suddenly in a dramatic fashion. This is a reference to the" Dramatic Chipmunk" meme -the squirrel moves in the exact same way with similar music.
Trivia: The logo on the floor during Korra's cage fight is the same one used in Earth Rumble VI in "Avatar: The Last Airbender"
Trivia: Dio in this episode drinks Cronenberg Whisky, just like in the manga. The fictional brand is most likely a homage to the director David Cronenberg, especially given the bit of 'body horror' appearing in this arc.