The term doesn't have anything to do with the size of the girls involved; although for the purists...that'd be the most accurate portrayal.
Guy 2: Dude, thats fucking epic!!!
Guy 1: Thats why I did it!!!
- Mate it wasnt just her, we were playing four player!
Ken: That's disgusting. She's so fat and I can't believe she went swamp ninja on him and took advantage of him. That's a hungry hungry hippo right there. Too bad she thought she was better than Enoc, he's a hungry hungry hippo too trying to crush Linda!
Person 2: Hungry Hungry Hippo!