An NPR piece on a study that looked at using guinea pigs to help autistic children interact in classroom settings.
Animals can be very calming for many people - when I worked at Bell Labs a group of us were working with some people in another part of AT&T along with a german shepherd. It seems one of the programmers was blind (!) and his guide dog always came to the meetings. She was extremely well behaved and would visit everyone as the meeting progressed. One of the best additions to a meeting I've seen.