Bulma: "I guess that's why you've never needed a haircut."

Goku: "Yeah, but I wish I could get rid of these split ends." ::rimshot noise::

Bulma: "Try shampoo." ::rimshot noise::

Vegeta: "I don't have time to listen to Kakarot's hair problems!"

Now this may leave some of you wondering -- what's up with Nappa? He's bald! The answer is that, like Krillin, Nappa shaves his head so that an opponent can't grab his hair in combat. He actually DID have hair once!... but we only see it in the Bardock Special... ;)