I only just learned the significance of A113 myself, working on a promo piece for Pixar's Cars 2. A113 was the room number for the animation class at California Institute of the Arts. Many alumni of the school use it in their projects. If you pay careful attention you can spot the number in nearly every Pixar film.
Check out the promo below and see if you can spot the specially made prop featuring the number. There are a few other fun things to watch for so don't blink. Also, next time you are watching Toy Story, or Cars for the billionth time, maybe it will give you something new to snag your interest. Keep an eye out and let me know where you spot A113 next.