Rio
At the beginning of my second year of grad school, I volunteered to raise a pup for Paws with a Cause, an organization that provides trained service dogs to people with disabilities. Rio was six weeks old when he arrived, and six weeks later he began visiting the Michigan math department, wearing his special blue foster puppy cape. He attended countless algebraic geometry talks, watched the professors carefully, and quickly learned the essentials of napping discreetly in the back of the seminar room. When Rio was fourteen months old, he went back to Paws to begin his official training, but lingering complications from his neutering surgery (poor guy!) eventually disqualified him from the program.
Rio returned to me as a civilian dog in 2004 and continues to visit friendly math departments, without his cape, whenever possible. He has served well as my unofficial TA, gently reminding students and teachers not to take themselves too seriously, and to take a break and go outside sometimes when the weather is nice. Speaking of which, it's probably about time for a walk in the hills, and maybe a nap in the sun.