I used to work at a place where a guy used, "Hello Fuckers" as test data. Our manager got a very angry call from a customer who printed out a 300 page report with, "Hello Fuckers" at the end of every line.
One of my former colleagues used to put weird error messages (made up words mostly, but really funny to pronounce). One of these messages escaped QA and went to a customer - but this was a nice guy, and he called up and asked what that word means (it was a while ago, can't remember the word now).
We didn't have anything to do one afternoon, so we searched google maps for names of funny places - there is a town called Hell. Imagine going there and reading the sign "Welcome to Hell". Good times were had at that job :p