I ask them their name. No matter what they say I say "No way, I know you, you're Sponge Bob!" When they giggle and say no you pretend to think very hard and guess a few other characters. They get all excited trying to make you say their correct name. They love "teaching" adults.
I also have a squeaker from inside a toy (there are places that sell the squeakers separately) I hid it in my palm and touch their shoes while pressing teh squeaker. They are amazed that their shoe squeaks. Warning: they may spend the whole shoot trying to squeak their shoes.
I have a monkey with really long arms. I come in wearing him like a cape. I tell them I need their help I lost my monkey. They say "It's behind you" You swing around and look but of course nothing is there because the monkey swings with you. You tell them no way, there is no monkey there and they crack up while you basically chase your tail trying to see the monkey.
