The Martian drones were performed by two people back-to-back in one suit. A little person was carried in a sort of backpack on the back of a normal-sized performer. The little person would operate the drone's mouth and smaller arms (as seen when the drones load their weapons) while the full-sized performer made the creature walk and used ski poles to move the longer arms (as seen when the drones "salute" Mrs. McKeltch). The full-sized performer faced the rear of the suit and had to walk backwards so that the creature's knee joints would bend in a "not-human" fashion when it walked. Several actors performed the drones, working in shifts, which meant each performer who did the "walking" for a Martian needed his own custom-made footwear.
Jimmy Hunt, who played young David MacLean in the original Invaders from Mars (1953) and the police chief in this remake, actually has more than almost a dozen lines, not just one as reported by a reviewer. When he and Officer Keeney go up the hill in search of Mr. Gardner, Hunt's line of "Gee, I haven't been up here since I was a kid" is a playful reference to the similar area of Martian activity that he witnessed as the boy in the 1953 movie.
Near the beginning of the film the parents are getting David Gardner ready for bed, and start shuffling things around his bedroom. The father picks up a magazine and starts to read it. The magazine was a late 70's slick fanzine called Fantascene. That issue had a very fine article on the making of the original Invaders from Mars (1953).
For the sequence where one of the Martian drones eats Mrs. McKeltch, a special "eating rig" consisting of just the drone's head (with chewing jaw movements) was built for the closeup shots. The rig was built on a "seesaw" device so the drone could throw its head back to swallow. A short burst from a hidden fire extinguisher provided the drone's post-meal belch.
Wade Williams had acquired the rights to Invaders from Mars (1953). For the remake rights, Williams received over 50 times the amount he had paid. Williams had already made a very handsome profit from the original film from television, cable and video releases.
The scanning device that Bud Cort uses in the elementary school basement is the same prop used by Saavik in Star Trek II: The Wrath of Khan (1982) when investigating the Regula I station with Captain Kirk and Dr. McCoy.
Only two Martian drone suits were made for the production. This is most noticeable in scenes where the Marines encounter drones in the tunnels leading to the ship. Clever editing and the use of a fully sculpted and painted but non-mechanized lighting "stand-in" drone (it can be seen coming up right behind David when Mrs. McKeltch sees David and threatens him) created the illusion of multiple Martian drones on the ship.
During the final shootout between the Marines and the Martians in the Supreme Intelligence's throne room, a fire broke out. It was quickly contained and no one was hurt, but quick thinking led to the Supreme Intelligence being cut open to let the puppeteers out.
The trivia items below may give away important plot points.
In the scene where actress Laraine Newman's and actor Timothy Bottoms's necks explode, the sparks caught the actress' hair on fire and singed a large part of it. She did not realize this until afterwards.