The production number "'Cause I'm a Blonde" was in the original version of the script, but it was dropped from principal photography because the producers decided to tone down the musical numbers. Six months later, they decided the movie needed the scene, so several cast members were brought back. Julie Brown was upset because she had gained weight, and the scantily-clad cast was physically uncomfortable shooting this beach scene during the winter.
Jeff Goldblum taught acting at the time, and inexperienced actors Jim Carrey and Damon Wayans would often go to him for advice. One of Goldblum's techniques was to distract himself before a take by reading aloud from a book right up until "action" was called, so Carrey and Wayans would make loud noises in-character between takes. Julie Brown said, "It wasn't easy to work with them, even though they're all really talented."
Much of the language that the aliens speak is actually just the dialogue being read backwards. This is particularly obvious with Wiploc during his conversations with Zeebo. For example, 'from' becomes "morf" and 'females' becomes "selamef."
Janice Dickinson was cast and co-starred in several scenes with Jim Carrey, only for them to be deleted without Dickinson being made aware; she didn't find out until the movie's premiere.