A young girl in a penguin costume sets off to pick out some birthday hats and gets a little carried away. Harriet lives in the big city with her two dads. On the day of her birthday party, Harriet puts on her special errand-running Penguin costume, and she and her dads head to the store to pick up party supplies. But when she encounters a group of real penguins Harriet gets a little carried away, and before she realizes her mistake she’s on a hot air balloon heading to Antarctica.