Connor's 5. It's that age when children start to tell jokes. They don't understand them, just tell them. Connor's favourite recently went:
"Knock Knock"
"Who's there?"
"Banana"
"Banana who?"
"Banana [insert random word]"
Follow with gales of over the top laughter.
So we bought him a joke book. The results are more amusing, but not for the right reason.