Peter Pegasus (also known as Baby Pegasus or Young Pegasus in certain sources) is one of the main protagonists in "The Pastoral Symphony" segment of the 1940 film Fantasia. He is presumably the youngest of his siblings, and bears the most resemblance to his parents, having his father's coat and his mother's mane, tail, and eye color.
He's a playful little foal, eager to get in on the fun, and fly with his family.
The character's popularity within the Disney studio lead them to consider utilizing him in future Fantasia segments before work on any Fantasia followups were cancelled. Some of these proposed pieces were "Invitation to the Dance" and "Flight of the Bumblebee".
Although he was referred to as Peter Pegasus during the film's production, the character was originally not heavily promoted with this name, and is occasionally referred to as either "Baby Pegasus" or "Pegasus" in certain materials and merchandise. Most materials relating to Peter Pegasus' name were related to the unfinished standalone segments and the name became more prominently used again when these materials were re-discovered in the 1990s during the research for The Disney That Never Was: The Stories and Art of Five Decades of Unproduced Animation and the name has found new use since.