The video below is not a setup. This guy, Gregory Pike hangs out in downtown Santa Barbara every day. From the Associated Students at UCSB website linked above:
"The dog raised the cat — I used her gestation period to raise the cat like a puppy. She chose Kitty from the litter, so she thinks it's her baby." The cat was then raised around all sorts of small animals, and treats the rat as if it were its own sibling. With the rat, "it's all about food." Rats, it turns out, are very open to interspecies pairing, as long as they aren't threatened and are properly taken care of. While it seems odd for the cat and rat to be stacked on top of the dog, Pike explains that it is the animals "safety zone": It is where the cat and rat feel most at home and protected by their surrogate mother. Of course, it also helps Pike and his pals walk around a little faster, as well as avoid possible rat or cat tripping incidents.