1. He burps and says; "That's the sign that the tank is full!"
2. He drinks (anything) out of a glass and asks "Got milk?"
3. He jumps on you and yells; "Cowabunga!!!" (Or the closest version of Cowabunga that he can pronounce.)
4. He bugs you for days to buy/make lasagna.
5. He randomly laughs all by himself, (remembering the funny parts).