Big Chungus is a fat version of Bugs Bunny which was shown in one of the Looney Tunes episodes. The episode first goes with a man and he tries to keep Bugs Bunny in his hole by blocking it off with planks but Bugs Bunny got out and looked like the man. It thus created BIG CHUNGUS. 
Videos and even a video game was made named Big Chungus which started as a joke with a fake cover of the video game with Big Chungus. 
Meme Heaven 