If a cat is crazy, a dog is not. If a dog is crazy, a cat is not. As from Alice in wonderland:
We're all mad here. I'm mad, You're mad.
Chesh: "To begin with, a dog's not mad, grant that?"
Alice: "I suppose so."
Chesh: "You see, a dog growls when it's angry, and wags it's tail when it is pleased. Now, I growl when I'm pleased, and wag my tail when I am angry. Therefor, I'm mad."