An expedition in the South Pacific lands on a tropical island where the natives worship the mysterious deity Gappa. An earthquake opens up an underground cavern and a baby reptile is discovered inside. The natives warn the foreigners to leave the hatching alone, but they don't listen and take it back to a zoo in Japan. Soon after, moma and papa Gappa start smashing Tokyo looking for their kidnapped child.
| Actor | Role |
|---|---|
 Tamio KawachiHiroshi Kurosaki | Hiroshi Kurosaki |
 Yōko YamamotoItoko Koyanagi | Itoko Koyanagi |
| YYuji OkadaDaize Tonooka | Daize Tonooka |
 Kōji WadaMashida | Mashida |
 Tatsuya FujiGeorge Inoue | George Inoue |
| KKeisuke InouePresident Funazu | President Funazu |
 Zenji YamadaCaptain of the Kamome-maru | Captain of the Kamome-maru |
| BBumon KaharaElder | Elder |
| KKōtarō SugieReporter #1 | Reporter #1 |
 Saburo HiromatsuHosoda | Hosoda |
| TToshinosuke NagaoCmdr. Riku | Cmdr. Riku |
| MMasaru KamiyamaThe Professor | The Professor |
| KKokan KatsuraSaburo Hayashi | Saburo Hayashi |
| SShirō OshimiOyama | Oyama |
| YYoko OyanagiAihara | Aihara |
| SSanpei MineIslander 1 | Islander 1 |
| TTakashi KoshibaReporter 2 | Reporter 2 |
| KKensuke TamaiIslander 2 | Islander 2 |
| MMinoru SatoReporter 3 | Reporter 3 |
| SSeiji MatsuokaIslander 3 | Islander 3 |
 Hiroshi ItoReporter 4 | Reporter 4 |
| MMike DaneenPetty Officer | Petty Officer |
| RRuich FidancerCaptain of the Sea Angels | Captain of the Sea Angels |
| PPaul SchemanProfessor | Professor |