Don't leavem in for too long. If they start blowing black smoke out, that means they've been in for too long. When one tears a Peep apart, one may then stick it back together in many positions. A few favorite variations are the 2 headed Peep, the Peep who's always looking behing him, the gooey innards Peep, and the Peep with no shape whatsoever. You can combine these basix to form your own special Peep friends.
Peeps are by nature, a very caring snackyfood.
I've found it really scares them when you tell them you've done something horrible to their Peepmates. This makes them really pissed, for most of their appeal is in their mallowyness.