I've seen several rather bizarre belly button tattoos over the years. That is one that someone will regret someday...though it is funny now! Some I kept on file for a laugh, Bart Simpson-Mooning, a monkey-mooning, and one is worse than the cow one posted here!
My Dad had one on the inside of his forearm of a "pin-up girl." When he flexed his fist just right the muscle on his arm would cause her to do an erotic little hula dance. He always had to wear a long sleeved shirt if he was to be in polite company.
I myself have refrained from the whim to get a tattoo due to certain physical "conditions" which would detract from the artwork immensely. A wriggling temptress on my arm at age 20 or so would now look like the missing link!