My 3YO DS has, predictably, fallen in love with the words poo-poo, pee-pee and stinky. What to do? Ignore it? My DH has trouble with that approach. But, of course, DS loves the attention he gets when he says one of those words, even if it is negative attention, so of course, he keeps doing it.
Also, what do you do when your rhyming-infatuated preschooler happens upon the f-bomb while talking about rhyming words? Duck, truck, cluck, muck, luck, f***. Ignore it and hope he doesn't say it at school, or that if he does, it is taken in the context in which it is said, i.e. a string of words that rhyme with it?