Yes, they are very morbid, but I've long had affection for "Mommy, Mommy" jokes. But I'll just put one of the less gross ones here. (This one also appeals to my love of movie monsters.)
"Mommy, mommy, what's a werewolf?"
"Shut up, and comb your face!"
(Aren't you glad I didn't do, "Mommy, mommy, what's a vampire?")