A man takes his dog to the vet. “My dog is crossed eyed. Is there anything you can do for him?"

“Well,” says the vet, “let’s take a look.” 

So he picks the dog up and examines his eyes, then checks his teeth. Finally, he says, “I’m going to have to put him down.”

“Why? Because he is cross-eyed?”

“No, because he’s really heavy.”