Just when William is ready to fall asleep in his cozy cabin, there is a tap on his window. A chilly chipmunk asks to stay, and Will scooches over in bed. "There's room for two -- I'm sure we'll fit." The chipmunk is just the first in a parade of mammals, each bigger than the last, until the bed is full. Then a note is slipped beneath the door: "Do you have room for just one more?" William tugs the door to see who's there . . . only to find a great...