The fourth book in the beloved and award-winning school hamster series! A classroom hamster has to be ready for anything, but suddenly there are LOTS-LOTS-LOTS of big surprises in Humphrey's world. Some are exciting, like a new hamster ball. But some are scary, like a run-in with a cat and a new janitor who might be from another planet. But even with all that's going on, Humphrey finds time to help his classmates with their problems. But will Mrs. Brisbane's unsqueakable surprise be too much for Humphrey to handle? Look for all twelve of Humphrey's adventures!