Due to stock-footage taken from previous movies, Godzilla's appearance keeps changing from scene to scene.
When Ichiro takes his radio out of the cupboard, there is a Godzilla toy facing the camera. In the next shot, the toy has switched positions.
Scenes of the giant spider Kumonga were taken from the film Son of Godzilla (1967). Since the original scene featured Minilla wrapped up in spider webbing lying next to Kumonga, a large rock of sorts was unconvincingly edited into the footage to hide Minilla, because in this movie Minilla is supposed to be elsewhere. But in one shot where Kumonga is seen from the back, Minilla is in plain sight trapped in webbing.
A few of the jet aircraft that Godzilla are shown to bounce off his chest. However, an actual jet would be destroyed upon impact. This takes place during a dream sequence, so reality may not be the truth.
When the monster Gabara is flung into the air and flips over, the effect was done by rotating the entire camera, thus the clouds and the background are spinning together with him.