Big Chungus refers to an image of the cartoon character Bugs Bunny, usually captioned with the phrase "Big Chungus" and presented as a game for PlayStation 4 console. The word "chungus" was coined by video game journalist Jim Sterling several years before the meme became popular.
The image of Bugs Bunny appears in Merrie Melodies cartoon Wabbit Twouble, first shown on December 20th, 1941[1]. In the short, Bugs is mocking Elmer Fudd, who in this cartoon was made much more portly than his previous and more iconic design (clip shown below).