P.T. Flea is Pixar Legend John Ratzenberger's favorite Pixar role, because "in real life, I always get a kick out of those kinds of characters, people who just go into a rage for [no] explicable reason. He was always on edge. His blood pressure was always way over the top, and everything that he did was done in a panicked state. So it was a lot of fun to play him."
In the bloopers shown at the end of the film, Princess Atta is shown cracking up during her scene with Hopper, ruining take after take until Hopper goes to his trailer in frustration. This is a spoof of Julia Louis-Dreyfus being known to do the same.
The Pizza Planet van from Toy Story (1995) that appears in every Pixar film is visible around 25 minutes in, just after the circus scene as the camera tilts up.
This is the first Pixar film to have outtakes. The outtakes were shown theatrically and on the VHS, but are only available in the bonus features on the DVD and Blu-ray versions of the film. The outtakes are also available on Disney+.
Molt was created for the film to provide some comic relief out of the more uncomfortable moments with Hopper, but it was decided to make him Hopper's brother when it was realized that Hopper would never allow somebody as witless and annoying as Molt to stay with the gang otherwise.
John Lasseter, Andrew Stanton: The two mosquitoes trapped in the light of the bugzapper ("Frank, don't go towards the light!" "I can't help it - it's so beautiful!") are the voices of the co-directors.