Sir Peter Jackson made all the alien latex masks in his mother's kitchen. As he frequently used her oven to harden the latex, his family was forced to have sausages for dinner.
Director Sir Peter Jackson shot the film on weekends over a four-year period with friends playing the lead roles. Jackson funded most of the film himself until towards the end of the shoot when the New Zealand Film Commission gave him money to finish his project after being impressed with what he'd already produced. There was never a script for the movie; each scene was filmed from ideas the director had come up with during the week.
Sir Peter Jackson constructed his own counterweighted steady-cam device for this film that cost only $15.
During a scene where Derek's van swerves off the road and runs over one of the aliens, Ken Hammon sat on the hood of a van because they weren't able to buy a camera mount for the hood. Sir Peter Jackson was driving, but neither noticed a tree stump hidden in the tall grass. The van stopped immediately from high speed, launching Ken and the camera into the air. Amazingly, both Hammon and the camera came out fine, but the former said, "We ain't doin' that one again!"
Doug Wren who played the Alien leader, Lord Crumb, died during post-production. Because of the non-audio filming, his voice was dubbed by a different actor.
Peter Jackson: Apart from portraying two large supporting roles as Derek and Robert, Jackson also appears as the voice of Minister with whom Coldfinger converses on the phone in the beginning of the movie.