Man takes his dog to the vet, and says, "Doc - I think my dog is cross eyed."
The vet says, "Let me have a look at him." He picks him up and has a good look at his eyes and teeth, and then announces to his owner, "I'm going to have to put him down."
Stunned, the man says, "Why - because he's cross eyed?"
The vet says, "No: because he's really, really heavy."
I got the joke