Jack Russell

Jack russell is a crazy small breed of the Gray wolf, if you hit him, he will hit you back.
In the picture above (or bellow, i dunno) you can see a dead jack russell, for a living jack russell never rest.

Human 1: He's running like a jack russell.
Human 2: See? he got tired, a Jack russell will never get tired.

Or:

Labrador: the fuck, why are you running in cyrcles?
Jack russell: I love you.