Please don't ask why. Just go to iTunes and spend your 99 cents downloading Jonathan Coulton's rendition of "Baby Got Back".
Even if you absolutely hate Sir Mix-a-Lot's version and, like me, think it set Seattle back a decade in the music scene, you still have to download this song. It's hysterical. And if you do find it enjoyable and want to sample some other Coulton music, I would also recommend "Tom Cruise Crazy", "Pizza Day", "Ikea", and "SkyMall". They're all fantastically catchy and funny and guaranteed to put a smile on your face.
Just be sure when you search iTunes for his stuff, that you type in his full name "Jonathan Coulton" since typing in just his last name will cause your search results to be polluted by the under-sexed histrionics of the devil itself, Ann Coulter.
Unless you're into that sort of thing, in which case I really hope I don't know you. Seriously, you're scaring me.