In ancient times, the Gappas would fight other monsters for survival.
All three of the Gappas share common characteristics, being based on various reptiles and birds, such as eagles and hawks. The second parent lacks a head crest, and has a flatter face compared to their counterpart.
An expedition to Obelisk Island by Mr. Funazu uncovers a baby monster, who hatches from an egg near a sacred temple. The natives plead with the skeptical scientists not to take the baby away, lest it anger the baby's parents. Sure enough, they take the baby away, and soon, inside the caverns, its two parents rise from the underground waters beneath the volcano, destroying everything in their path. Saki, the only survivor, is rescued by an American navy fleet and brought back to Japan.
The parents storm across Japan, destroying all in their wake, but their assault ceases once they recover their child. Mercifully, they relent, and depart to return to Obelisk Island.
- The Gappas can fly at mach 6.
- The Gappas have an underwater speed of 150 knots.
- The Gappas' wings can emit hurricane-force winds.
- Both Gappas can fire a heat beam from their beaks that can burn and melt anything it touches.
- Main article: Gappa/Gallery.
- Tsuburaya Productions originally had an idea of a space bird monster that protected Earth in times of need, called Bemlar. The 'Bemlar Birdman' shares many traits with the Gappa, and caused rumors of being sold to Nikkatsu Corporation. However these rumors are false, as the design was recycled for another Tsuburaya monster called Hydra.