Oodako is a giant octopus daikaiju that debuted in King Kong vs. Godzilla (1962) and returned in War of the Gargantuas (1966). He's also known as the Daidako (Giant Octopus) and The Giant Devilfish. He also appeared in an alternate ending for the movie "Frankenstein Conquers the World" (aka: "Frankenstein vs. Baragon") (1965)
King Kong vs. Godzilla
One night Oodako crawled ashore on Farou Island and attacked a village hut in an attempt to get the special soma berry juice, that the natives store there. The natives and the pharmaceutical company team attacked Oodako to stop it, but failed. Then King Kong appears behind a giant wood fence. He crumbles the fence with his bare hands and throws the pieces at Oodako. Kong grabs Oodako, but the octopus holds tight on to Kong's head. There is a short struggle and in the end, Kong pulls off the monster and throws it to the ground. Then he throws two boulders at Oodako's head. Oodako flees back to the beach and presumely returns to the sea, and Kong beats his chest and roars in victory.
Oodako also appeared in the title credits of Final Wars as the narrator talks about the numerous attacks on the world by the Kaiju. (Stock footage.)
War of the Gargantuas
In War of the Gargantuas, Oodako attacked a fishing boat, but it was defeated by the Green Gargantua, Gaira.
Frankenstein Conquers the World
In an alternate ending for Frankenstein Conquers the World, after Frankenstein defeats Baragon, instead of being swallowed by the ground, Oodaka comes from the sea to fight Frankenstein. Frankenstein fights hard, but can't compete with Oodaka's numerous and sticky tentacles. Oodaka drags Frankenstein in to the water, seemingly to his death. After which, neither monster is seen again, in this movie.
Trivia:
Oodako is the only non-important monster to ever appear in three movies.
