"Hey look, I'm a vet. I don't need to ask my patients these kind of questions. I can tell what's wrong just by looking." He smugly added, "Why can't you?"
The doctor nodded, stood back, looked him up and down, quickly wrote out a prescription, handed it to him and said, "There you are. Of course, if that doesn't work, we'll have to have you put to sleep." [an error occurred while processing this directive]