"Why don't dogs and cats get nose bleeds?"
"Which is worse: fire in your bottom or spikes sticking in your bottom?"
"Where did lice come from?"
"Who's stronger, God or Santa?"
"Why aren't dragonflies purple?"
"How come [...] downloads movies which you shouldn't do but she's a good person?"
"What's more important, a volcano or your kids?" [huh?]
"How come dogs don't have to clean their teeth?" [actually, ours should]
"How come you NEVER let us do anything fun!" [huh? how did that sneak in there!]
What are some good questions you've had from kids?