A while ago I heard a funny knock-knock joke that went a little something like this:
"Interrupting Cow - "
Oh, hahhahahahhahaha!!! Love that joke!
and then what happens when you teach that to a couple of 6 and 9 year olds is a) nonsensical knock-knock jokes galore or b) constant interrupting
with a simple and very loud "Mooo!" right smack in the middle of anything and everything you're trying to say.
It's a big bowl of fun. Trust me.