CAN'T WE ALL JUST GET ALONG? THAT'S THE MESSAGE GREG Pike was trying to spread as he walked the streets of Washington. His mouse, Mousey, sat on the back of his cat, who was on the back of his dog, a Labrador/rottweiler mix. It made for a striking scene, as Pike led the trio through lunchtime crowds.

"We're on a world-peace tour," Pike told passersby. For $5 each, he sold holiday cards bearing a photo of the animals cuddling. The profits provide money for the tour.

Pike and his trio had driven to Washington, via the Florida Keys, from Taos, New Mexico, where he runs an animal shelter. He says the three animals never fight among themselves.

Why don't they try to tear one another's heads off?

"People are complicated," Pike says. "Animals, they're simple."

Pike, 38, an Army brat born at Fort Eustes, Virginia, was lured west by the mountains. He's always loved animals and spent many hours reading about and observing them. On a ski slope two years ago, he had the idea of stacking three animals atop one another.

"I started thinking, what can I put together that people will look at and be amazed?" he says. "I had just seen the movie Stuart Little--about a talking mouse. "I thought, I'll stack a dog, a cat, and a mouse."

To teach the animals to "stack," Pike devised a plan involving gestation periods--and a bit of trickery. When the dog went into heat, he let her run in the neighborhood "to have some fun" with other dogs. A couple of months later, at the end of what would have been her reproductive cycle, Pike placed a kitten in front of the dog one morning.

"She thought the kitten was her own," he says.

To get the cat to ride on the dog's back, he waited for a snowfall, then put the animals outside. The cat hated the feeling of the wet snow on her paws. To avoid it, she sat on the dog's back. The dog was trained to remain calm with a harness on her back, providing a place for the cat to sit.

Training the mice--there have been several--was easiest. Mice feel secure around their own smell. Pike placed a second harness in the mouse cage to absorb the scent. With this harness secured to the cat's back, the mouse stays put.

After Washington, the animal caravan headed for New York. Pike wants to help take care of the pets who lost their owners at the World Trade Center. On the long drive back to Taos, the dog will pass the time chewing rawhide while the cat nibbles on her favorite snack, dog biscuits. And there will be a happy homecoming when all the animals are reunited with their other friends at home--a cockatiel, several other mice, and a rat.

It took a year for Greg Pike to train his dog, cat, and mouse to sit on top of one another. Now they're a happy family.