Ambrose Walnut is a young and energetic squirrel from the Walnut Squirrel family. He is very small for his age and loves to jump, especially in puddles after rain. Ambrose looks up to his older brother, Ralph, and admires his father, Cedric, who believes Ambrose will go on to do great things. His father once built him a special treehouse with a log ladder, swing, slide, and hammock that Ambrose could manage on his own, which became a favorite spot for hosting friends. Ambrose enjoys imaginative play, such as pretending to run a supermarket with other babies, and he has tried making music on a violin and cello with a friend. He often wears a yellow tulip hat and a pink rucksack. Ambrose appears in stories that include a birthday party for Mrs. Periwinkle.