Edit for those who have never seen the full series of commercials: Long Long Man ends up marrying the dude who is always with the gal who is always lusting over Long Long Man
If you're thinking of the joke about the professor of deductive reasoning, I've always heard it as a doghouse, but I'm sure there are variations. Only 8 billion people on Earth, after all ;-)
Hmm, now that you say that I'm either fabricating a memory or we have two parts of a whole. I seem to remember no lawn mower leading to doghouse somehow?
I'll have to look it up when I'm off work if I remember