A couple of recent favorites:
On radical hair:
K. (from next door): Does my hair look radical?
Z.: What does "radical" mean?
K.: It means all messy.
Z.: No, your hair doesn't look radical. It looks like a girl's hair. Kind of... (pointing towards his shoulders) down.
K.: Oh. Okay. Good.
On death and God:
Z.: Daddy, are you going to die?I'm still kind of mystified by this one.
Me: Well, everything that's alive dies some day. So, yes. Some day I'll die.
Z. (slightly tearful): But I want to stay with you.
Me: Well, hopefully, it won't happen for a very long time. Years and years.
Z.: Well, we die when we tell God we're ready to die. Right?
Me: Uh... who told you that?
Z.: (after a long pause) God.
Me: Um... ah... I see.
On discovering a hidden cache of cookies (hidden by me):
Z.: Daddy, why did you hide the cookies?He's got a point, I suppose. Not that he's allergic to anything else, either, as far as we know.
Me: Because I didn't want you to ask me for one. Every time you see cookies, you ask for one.
Z.: That's because I'm not allergic to sweets.