The Luxo Ball (a.k.a. Pixar Ball), first appeared in the Luxo, Jr. short as a prop for Luxo, Jr. Since its debut, it has made numerous cameos in other Pixar films, most prominently in the Toy Story films.  You can own it now.  Straight from Disney Parks.

Disney Parks Pixar Pier Pixar Luxo Jr Bouncy Ball

• 4 inch diameter
• Imported