Harriet Ziefert is a children's author born in 1941 in New Jersey. She has written several hundred children's books, including the Little Hippo series. Ziefert and illustrator Emilie Bon have collaborated on a series of "Little Hippo" books, the first of which was published in 1988 by Viking Penguin. The books are written for children between 1 1/2 to 5 years-of-age. They are intended to help children deal with change, like the addition of a new baby to the family or moving to a new house. Her titles include Little Hippo's New Baby, Little Hippo's New Friend, Little Hippo's New School and Grandpa, Will You Play With Me?