Monga's name comes from the name of the Japanese flying squirrel, the momonga.
Monga is a monster that would have had dark-blue fur, membranes between his legs, ox-like horns, and a mace-like object on the end of its tail.
Much like Varan, Monga's sole known ability was that it would be able to glide around using the membranes between its limbs.
- Monga was replaced by Space Gyaos in the finished film, likely for budgetary reasons. Daiei chose to simply repaint the Gyaos suit from Gamera vs. Gyaos rather than create an entirely new suit for Monga.
- Monga is one of two unmade kaiju to be based on flying squirrels, with the other one being Nikkatsu Corporation's Momonra. It is unknown if this is more than just a coincidence, as Momonra's debut film was going to be released in 1966, 3 years before the release of Gamera vs. Guiron.