When Tom and Lucy Little, tiny humans with tails who live hidden in the Bigg family's house, get an assignment on animals during their teacher's monthly visit, they go to see the Biggs' pets and try to get an egg from the henhouse.
While trying to start new friendships in the first grade, six-year-old Lily gets in trouble with her teacher, but she soon discovers that it is possible to start over again after making a mistake.