A pool was set up on stage nine during the production (stage nine is one of the largest on Toho's lot in Setagaya). They used the pool, which was about five feet deep, to film the shot of Godzilla rising above the surface of the ocean. Haruo Nakajima (the actor in Godzilla suit) was on a cart on a rail. He held onto the handle of the cart while it was towed by a truck. As the cart moved forward, he slowly rose out of the water. He wore a very tiny air cylinder that contained enough air for about ten minutes. The water that rushed by his face while the cart was being towed made it very difficult for him to prevent the mouthpiece from coming out of his mouth.
Godzilla's look transformed from a part menacing-like look into a loving father after Godzilla vs. the Sea Monster. By this time, it became obvious that Godzilla movies were now being made to suit children. In Godzilla's new look in Son of Godzilla, his eyes were made larger and his snout shorter. The shape of his head resembles that of a human head, probably, to make Godzilla less scary. The tone for Son of Godzilla was a playful and goofy tone, and Godzilla's look contrasted with it beautifully. This suit was later used in Godzilla vs. Gigan in the swimming scenes.
Japan Import DVD has Super-8mm version (Japanese Audio), as a special feature.
Much of this film was done on Guam not only to take advantage of the island locale, but to save money by not having to build costly miniatures.
Scenes from this movie are later seen in "Godzilla's Revenge," and "Godzilla vs. Gigan."
The deisengoji suit is used in this movie os a stunt/water suit. It first appears when we first see Godzilla at the begining of the movie after the showing of the title. Then it is seen in the very next Godzilla sighting as he rises out of the water responding to Minya's call out to Godzilla to save the little monster.
The name Minira started out as an inside joke short for "Mini-Gojira", because the film crew saw him as a "miniature Gojira". For the English dub, the name was translated to Minilla, meaning "Mini-Godzilla".
This was the second film of the Godzilla series to be sold directly to TV (the first one was Godzilla vs. the Sea Monster (_Gojira-Ebira-Mosura: Nankai no daiketto (1966)_