Clifford

We went to the store together as a family. When we were done, David needed to go across the highway to the hardware store. He took Meleah and Davey with him, and Julia, Lydia, George and I waited in the van. I was enjoying their profound conversation. Here's a snippet...
Julia: I like Clifford. He's big and red. He doesn't go poo-poo.
Lydia interrupts: He DOES go poo-poo. 'Cause Clifford is a dog, and dogs go poo-poo.
Julia: Dogs go poo-poo, but not Clifford. 'cause he's not a real dog, he's a pretend dog, and pretend dogs don't go poo-poo.
Lydia: Well, he's a dog, and dogs go poo-poo.
... and on and on...

Right when I thought they were going to erupt into screaming and crying, they changed the conversation...just in the nick of time!

So, please, post YOUR opinion. DOES Clifford go poo-poo or not? Please explain and back it up with proof.