Gene Simmons of the band 'KISS' currently owns the prop severed head of the kid's mother. It was given to him by Tim Sullivan when he interviewed Simmons for "Fangoria" in 1983. Sullivan - who was a PA on this film - went on to produce Detroit Rock City (1999) and write and direct 2001 Maniacs (2005) and Driftwood (2006).
There's an unofficial sequel, Metamorphosis: The Alien Factor (1990). In many parts of Asia, it was distributed under the name "The Deadly Spawn 2: The Metamorphosis". Because Metamorphosis was made for millions of dollars more, and had much higher production values than the "Deadly Spawn" did, the producers of both films wanted to separate them altogether.
The effects of the mini-spawns slithering across the floor in the basement was achieved by cutting a "S" wriggle into the floor, and pulling the spawns along under the floor.
For the first sequence involving the monster, in which it is mostly off-screen, only a shadow is shown; the effect was produced with a simple cardboard composite, projected onto the tent. The Spawn is next seen when it attacks and violently devours Charles' parents. This stage, nicknamed the 'Mother' Spawn or the 'Mama' Spawn by the special effects crew, was created as a full-size mechanical puppet. It was first sculpted in clay and then moulded. The mechanical understructure, which featured rough mechanisms allowing jaw closure for its three heads and arm movement, was covered with a skin made in sheet foam rubber. Said skin was draped with liquid latex-coated paper towels; this gave additional texture to the Spawn's skin. The monster's overlapping teeth were instead moulded in actual dental acrylic and polished with powdered pumice stone. "I really wanted to be a dentist," Dods jokingly commented. The 'Mama' Spawn was built in John Dods.' basement; when the time came to bring it on set, the crew realized that it was actually too large to pass through the doorway that led to the shooting set. One of the puppet's three heads was thus removed, only to be reassembled onto the main body once inside the set. For the 4-5 shots from the inside of the Spawn's maw, a specific camera rig was built with rough mechanisms that enabled the jaws to open and close.
This film was almost picked up for theatrical release by Paramount.