The difference between boys and girls

I was at a barbeque last night with HP and lots of people from my church. I spent part of the evening chatting to a lovely young man (and when I say young I mean it - he's the youngest son of Adrian Warnock, and is 3 (I think)).

We were sat on crossed legged on the floor and I had his plate of crisps ("I want blue crisps" - salt and vinegar pringles) on my lap while he drank his juice. He suddenly said "that's your lap" (pointing to my lap), I agreed that this was the case, and he went on to say "you're a girl, you've got a lap. I don't have a lap. Boy's don't have laps and I'm a boy".

I couldn't stop laughing after that, just why he should think that boys don't have laps is beyond me! Still, it made my evening that extra bit funnier, so I was willing to say "oh I see, that's interesting" and continue to listen - after all, what other things might I learn about the differences between boys and girls?!?!