Trying to figure out who stained my pants with their discarded hot dog carcass, was what he wanted to say, but Keaton's appearance distracts him. A dog-person hybrid? This was very confusing for him. Part of his brain wanted to pet the dog, while the other part thought it too weird because he wasn't all dog, and also adamantly wanted to yell at him for littering.

These two parts of his mind get their wires crossed and he said, "What the dog litter?" Does he realize what he'd said? No.