John Carl Buechler was considered to direct the film, and his version of the story was going to be a straight up horror film, in which the Garbage Pail Kids would have spawned from radioactive sludge that had found its way to a garbage can filled with broken dolls, turning them into serial killers.
The garbage pail kid facial puppet heads (masks) required more detail work for facial animation prior to filming. The heads were not properly completed by the effects team because of financial reasons and the time factor related to filming. Rod Amateau, in-spite of the unfinished heads, made the film on schedule, expecting the puppet head effects animation to improve during the film schedule.
Mackenzie Astin auditioned and signed onto the movie without telling his father, actor John Astin. When he was informed and given the script by his son, John Astin thought the script so poor he looked into getting Mackenzie out of the film.
Filmed in a Van Nuys warehouse off of/behind north of Sepulveda Blvd. during the hot summer months requiring air conditioned facilities for both (front of warehouse) production office, costume, dressing rooms, with the stage area located behind. The exterior backside/rear of the warehouse building was adapted with a street shop facade tied with the interior shop (set on stage). Anthony Newly's dressing room trailer was located opposite the warehouse back-street facade. The shop interior, and basement sets were permanent, while the motorcycle gangs' bar, fashion show were swing sets, clearing space for the other film sets constructed for the film. Other locations were within a ten mile radius of the home base warehouse stage.
In the basement of the antique shop where the Garbage Pail Kids hideout, there's a large painting by the stairs. In the painting is the makeup creator, John Carl Buechler, and to his right is a small green creature. That creature is the eponymous character from Ghoulies, for which Buechler designed the characters a few years prior to The Garbage Pail Kids Movie.
Bob Jillson and Hub Braden really enjoyed working with the director/producer Rod Amateau because he "appreciated" their effort and work on his project. Purposely interjecting humorous details and touches into the sets and the set dressing, Rod always picked up on their treatments. An example was the biker bar set. After researching a West Hollywood biker bar, the top of the bar imitated the actual biker bar...dressed with a chorus line of teddy bears. The peanut barrel was a child's toy chest, a giant open top football filled with peanuts for the cast to eat and to throw. The side wall with bike parts and wheels (like a mad bike sculpture) blowing out of the wall with police boots extending over the handlebars, fenders, and wheels. Amateau went nuts with laughter having a great experience filming the scenes in the set.