Apparently some pros have done porn comics. I heard (as in I wasn't there) of a guy talking to a pro and recalling fondley his work in said porn comic. The creator (embarrassed or whatever) denied it and said the fan most have been mistaken. The fan brought the porn comic to show him the next day at the show just to stick it to him.
On a side note the nicest thing I've ever seen by any one pro was when I commissioned Mike Weiringo to do a fully inked spiderman illustration for my girlfriend's birthday, it came out amazing, when I went to pay him Mike just smiled and said "I ain't taking your money kid". No matter how much I presisted he refused to let me pay him. It was my first con(at a hotel in Houston), the first time I got a sketch from a pro, the first time getting crits on some sequential samples too, that experience...Mike's kindness and generousity really made me want to become a part of the comic book making world. He really was the nicest guy in comics.