In the first full-length Pixar movie, Toy Story, Woody and Buzz hitch a ride on a Pizza Planet delivery truck and wind up at the insane pizza arcade. Ever since, the beat-up yellow truck has appeared in every single subsequent Pixar movie (except The Incredibles).
In A Bug's Life, it's parked in a field, next to a trailer, "above" Bug City. (When Randall is banished from the monsterworld in Monsters, Inc., the exact same shot recurs in Monsters, Inc., but the trailer and truck are in much better shape.) In Cars, the Pizza Planet truck is a living, breathing creature with eyes who attends the big Piston Cup race.
They've got Pizza Planet in Paris! In Ratatouille, it can be seen in the background of a city scene, driving over a bridge. It's also a broken-down relic of earth's excesses, showing up in a pile of junk and debris in WALL-E.
Brave's animators had to get a bit more tricky, since the movie takes place in medieval Scotland. It appears as a wooden carving on the Witch's table. Finally, it's also inside one of the hundreds of happy memory orbs in Inside Out.
