I do remember hearing about a frat activity called "hogging" a few years ago.  It was a contest where all participants went out to bars as usual to pick up girls, but the winner was decided by who banged the fattest one.    Now this may actually be as much of a myth as rainbow parties, but it be far from the most ridiculous thing frat guys have ever done.  It may have even been part of hazing (e.g. you must bang a girl who is at least 300 pounds in order to prove your allegiance to this frat).