Sebastian is an alley cat who is usually reduced to janitorial duties and likes to nap any chance he gets. He sometimes tricks others (usually Q.T.) to do his own work, but sometimes his tricks backfire on him. In the side show, he has a ventriloquist dummy called Sly with him.
Sebastian was with Dumbo and Lionel when they first started out. According to him, his mother asked Mrs. Jumbo if Dumbo would watch over him.