This is the only film in the series to not feature a child as the main human character.
Japanese monster movies were often given bizarre translations in Germany. Most notably, references to the character Dr. Frankenstein were inserted into many of the movies released by Toho Studios, primarily their series of Godzilla films. As well, Godzilla characters like MechaGodzilla or Jet Jaguar were infamously renamed to King Kong. The German version of this movie carries one of the most bizarre such changes: Gamera is renamed to Barugon, and the actual Barugon is renamed to Godzilla (pronounced "Gochilla"). The movie was even given the alternate titles "Godzilla, der Drache aus dem Dschungel" ("Godzilla, the Dragon from the Jungle"), "Godzilla, Monster des Grauens" ("Godzilla, the Monster of Horror") and even "Gamera vs. Godzilla". Confusing matters further, on one of the bootleg VHS covers, Gamera is shown fighting against the American Godzilla from Godzilla (1998) instead of Barugon. The film was released in Germany with certain scenes cut, so when these missing scenes were dubbed for the later DVD release, these changes were still kept, including the botched pronunciation of Godzilla.
The first Gamera movie in color.
The first draft of the script didn't have any references to the first movie.
The film was initially meant to be more adult-oriented, with the native island dancers appearing topless. While the movie was relatively serious and had some more adult moments such as intense fights, in the end the movie was released with child audiences in mind.
Onodero's mistress wasn't in the first draft of the script.
The original idea for the film involved ice-based aliens invading Earth and oppressing humanity. Another idea the studio considered involved an ice giant from Scandinavian folklore. Eventually, the ice concept was carried over into Barugon's freezing ability.
The original script featured a more elaborate opening scene, and Gamera's rocket would have crashed to Earth before he escaped.
Since the Barugon suit wouldn't sink, it had to be cut into bits for the final scene when Gamera drags him into the water.