Nope, that's real. Mozart was actually famed for having a few weird songs about farting and general scatophilia, kind of weird really.
In my first year at Sheffield Uni, we changed the Sheffield Hallam (rival "uni" (poly)) wikipedia to have Ian Huntley as one of their alumni. it was fucking hilairiious, until they clocked it and changed it about a week later
i can't find any decent versions of this with lyrics etc on youtube, there's one but it just plays with no audio