This is my favourite Vet joke of all time:
A man takes his Rottweiler to the vet and says, "My dog's cross-eyed, is there anything you can do for him?" "Well," says the vet, "let's have a look at him." So he picks the dog up & examines his eyes, then checks his teeth. Finally, he says "I'm going to have to put him down."
"What?, Because he's cross-eyed?" "No, because he's really heavy."