Production
Pre-production designs of Maurice and the main little monsters were created by Alan Munro, previously known for his work on Beetlejuice.
Principal photography took place from August to October 1988, in Wilmington, North Carolina. Interiors were filmed at DEG Studios (later EUE Screen Gems, and now owned by Cinespace Studios). The monster underworld, the toughest portion of photography, was filmed primarily at the abandoned (and some say notorious) Ideal Cement Plant in Castle Hayne, North Carolina. Many of the stairs and bridges were actually built within the plant; some stairs reaching 20 to 30 feet high. A second unit, also working at the cement plant, created and filmed miniatures for forced-perspective shots with the life-sized sets. Production days at the cement plant totaled 1/3 of the film's principal photography - which went 16 days over schedule due to longer than expected filming at the plant.
Reminiscing about filming at the cement plant, gaffer Jock Brandis told the Wilmington Star-New's Cape Fear: Unearthed podcast in 2021:
"We used to call it Stage 13. It was bad luck. No one wanted to be out there. The reason we used it was because it was this amazingly flexible place; these huge, cavernous spaces made of concrete and steel with walkways and conveyor belts and tunnels and just this fanciful stuff. And you could basically turn it into anything. It was great because the world in Little Monsters was this mythical magical world underground, where it's eternally night and kids who were smart enough could figure out that there was a portal under their beds. It was a world of eternal fun and games and snacks. We had to do this strange underworld thing, so it was video games and weird walkways, catwalks and tunnels. The beauty of it was that it was an indestructible building, so there's nothing you could do to damage it. Even if you're filming inside a stage and you're doing explosions or you're doing collapses, you could destroy the inside of a soundstage. There's no way you could destroy the 3-foot-thick walls of the cement plant."
Other key locations were the Wilmington National Cemetery, Wrightsville Beach, and Forest Hills Global Elementary - where the infamous “Who put piss in my apple juice!” scene was filmed.
The film has at least three known and unreleased deleted scenes. According to one of the film's set production assistants, Steve Head, a sequence in which little monsters use a flamethrower to "clean" an underworld dining room was filmed but deleted from the movie. It was a continuation of the dining room scene that ends with Maurice putting a chocolate cake in his jacket; and it introduced the flamethrower that Maurice uses in the third act. "It must have taken us at least half a day to film that one shot," he said. "The local fire department brought one of their trucks out to the cement plant. It was on stand-by in case anything went wrong. We did one shot and it was great. No problem. Gary Bierend was the Special Effects Coordinator. He operated the flamethrower. Will Purcell assisted. I don't know why they cut it from the film." A monsters' underworld filing room scene was filmed and deleted. Some of its filming can be seen in the behind-the-scenes footage on the Vestron Video Collector's Series Blu-ray. And according to the film's special effects make-up supervisor, Robert Short, another filmed and deleted sequence was an evil toy clown scene. The clown, puppeteered by Short, springs out of the floorboards and threatens Brian, Todd and Kiersten after they enter Boy's room.
Post-production visual effects were created by director Richard Greenberg's company R/Greenberg Associates (now R/GA) in New York.
