John Hora, who had previously worked as Joe Dante's cinematographer on all of his movies, was cast as Ozzie after Steven Spielberg suggested him to play the absent minded professor. Director Dante and producer Michael Finnell were very skeptical about that idea and Spielberg insisted that they give him a screen test to just to see and was cast after impressing Dante and Finnell.
All of the cells seen outside the pod were in fact made out of Jello according to Peter Kuran, the special effects supervisor.
This is the only film directed by Joe Dante to win an Academy Award. It won the Best Visual Effects award.
(at around 54 mins) When Jack is making his way to the mirror so Pendleton can have a look at his face a hiccup previously recorded by Mel Blanc which was used in various Warner Bros cartoons can be heard.
After Scrimshaw and Canker are shrunk 50%, there are a few scenes where they are seen with full-size actors. These shots were filmed using forced perspective. For the car scene, the rear of the car is actually twice as large as a normal car rear, and was about 20 feet away. During the scene half size hands and double-size heads were used. Using this method, the film-makers didn't have to worry about compositing two separate shots in post production, so the shots could be completed quicker. Even in the final scene with the suitcase, the case was twice as large, but the hand that closes it was real, closer to the camera in sync with the closing. It took about 20 takes before it was perfect.
Arthur Kane: (at around 56 mins) Arthur "Killer" Kane, bass player for the infamous New York Dolls makes an appearance as a passenger when the Cowboy is first seen in the airliner.
Joe Dante: (at around 20 mins) as the first employee in the Vectorscope Lab attacked by the techno-terrorists.
Joe Dante: [Looney Tunes Sound Effects] Sound effects lifted from classic Warner Bros. cartoons are used multiple times throughout the movie.