Liam's observation of the day: he was asking me how your arm makes the farting noise when you 'flap' it (you know what I mean, esp if you happen to be a 7 year old boy). I didn't really have an explanation so he offered this:
"You have a bone in your arm, and it has a button on it. When you move that bone, you press the button, then it makes the farting noise. But don't tell my mom."
Sounds logical to me!