Yeah, I don't really get it either. I really don't think there is anything to get. Its seems like just another redundant example of how to be vulgar (as if movies like Team America aren't enough)
and to exploit the main points of taboo, fucking your sister shittin/pissin in your families mouth? come on man thats plain wrong and truely vulgar... lol i dont think thats much of a joke but humorous.
almost like in Monty Python's The Meaning of Life, the part when the fat guys eats that last thin mint. It makes you laugh so hard but makes you wanna puke at the same time.
I believe that wikipedia's reference to it being an anti-joke basically means that its just such a shitty excuse of a joke that it's funny on some level. Vulgarity really doesn't entice me to laugh though. If it were really just an embarrassingly terrible attempt to be a joke then I'd probably laugh though.
See my Zelda CD-I topic in the youtube videos section to get and idea of what I'm talking about.