He has his father's wit.

Spencer: Can I have a treat for an after school snack?

Mom: I bought Ding-Dongs at the store. Do you want a Ding-Dong?

Spencer: What is a Ding-Dong?

Mom: You know, those chocolate covered cake things with frosting inside. A Ding-Dong!

Spencer (with a sly smile on his face): Hmm...Ding-Dong...doesn't ring a bell!

I totally cracked up. He knew he was making a joke. He is becoming very quick witted.