Found on EK’s LJ:

Q: How many scene kids does it take to screw in a lightbulb?
A: It’s a pretty obscure number. You probably haven’t heard of it.

Q: How many DBZ characters does it take to screw in a lightbulb?
A: One. But it takes about five episodes. (Note: This joke also works if you replace DBZ with Bleach, IMO.)

Music and anime humor. Can’t go wrong, there, eh?