When the two soldiers are skeletonised by Jiger's heat-ray, the elbow joint on the leading skeleton is anatomically incorrect (the upper and lower arm bones appear to overlap).
When Jiger uses his heat ray and burns the second circle, the image freezes as the ray hits (watch the cars on the highway)
During the slide show the man identifies a stone monument as Stonehenge, but the pictures are of the city of Tiwanaku in South America.
More than once during their battles, Gamera lifts up and drops Jiger down to earth, even though Jiger itself is shown to be able to fly.
While sailing down Gamera's throat, the know-it-all kid mistakenly refers to the 'uvula' as 'tonsils'.