* CreatorsFavorite: The late Creator/HaruoNakajima put Gaira as his favourite role besides Franchise/{{Godzilla}}, as Gaira's more humanoid appearance allowed for a greater range of expression through the suit.
* HeyItsThatSound: Gaira and Sanda both share some growls and screams with Frankenstein, but Gaira's main roar is modified from that of [[Film/KingKongVsGodzilla King Kong]].
* WhatCouldHaveBeen:
** Not only did Sanda and Gaira not have names, they didn't even have their signature colors that really sets them apart in the final film. Sanda was the white haired "Mountain Frankenstein" and Gaira was the grey haired "Sea Frankenstein". It's likely this was a reference to the story the film was based on "The Sea Boy and the Mountain Boy". The film itself was also originally titled 'The Frankenstein Brothers' and instead of seemingly retconning some events, it was undoubtedly a sequel to [[Film/FrankensteinConquerstheWorld Frankenstein vs. Baragon.]]
** There was also a planned sequel where a Gargantua would've fought the Showa Godzilla.