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.
DIRECTOR_CAMEO(John LasseterAndrew Stanton): The two mosquitoes trapped in the light of the bugzapper ("Harry, don't go towards the light!" "I can't help it - it's so beautiful!") are the voices of the co-directors.
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."
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.
The original "teaser" trailer for this film was made up of animation made specially for the trailer and not appearing in the final film. This became a Pixar trademark.