Pixar strictly forces its animators to hide the alphanumeric code A113 in nearly every single movie they produce as an elaborate inside joke.

A Classroom Number That Became a Calling Card

A113 began as an ordinary room number at the California Institute of the Arts, where generations of animators studied. For alumni who went on to make films together, slipping the number into a scene became a way to nod to that shared beginning. The joke works because it is both personal and unobtrusive: most viewers can follow the story without noticing it, while those who recognize it get a small bonus.

How the Number Fits Into a Film

A113 is easy to hide because animated worlds are full of numbers. It can appear on a vehicle’s license plate, a door, a piece of equipment, or another background detail. Artists can add it without changing a character’s choices or interrupting a scene, so the reference can travel from one setting to another while remaining easy to miss.

It is better understood as a recurring in-joke than as a plot device. Nor does its appearance mean every film must contain it: the number is a familiar tradition, not a requirement that viewers need to hunt for. Its staying power comes from how little it asks of a movie. A tiny classroom code can quietly connect the people making a film to the place where many of them first learned the craft.