gappa: the triphibian monsters (1967)

aka Daikyojû Gappa.
"A monster!"
A Japanese theme park wants to stock up on some exotic animals and sends some people to a South Seas island to gather some. The island is home to a tribe that worship the mysterious deity Gappa, and initially welcome the Japanese expedition, until a baby reptile appears following an earthquake. As despite their warnings, the scientists decide to take the creature back to Tokyo. So they only have themselves to blame when mom and dad turn up looking for their kid.
A Kaiju that doesn't look on the creatures as monsters, but as doting parents, and lacks much of the crash, bang, wallop of others in the genre.

monster from a prehistoric planet (1967)

aka Daikyojû Gappa. Gappa the Triphibian. Monsters. Gappa, the Triphibian Monster. The Giant Beast Gappa. The Triphibian Monster.
A childlike version of UK monster flick Gorgo, where an expedition to a tropical island find the natives worshiping the beast Gappa. An earthquake reveals a baby reptile, and the exhibition leaders decide to take it back to Japan, with tragic consequences to the negro section of downtown Tokyo!
Not the greatest Japanese monster movie and some speculate that this is deliberatly bad and is in fact a spoof of the Kaiju genre, but I think it's a Japanese monster movie not Shakespeare! If you like wanton distruction by men in rubber suits and Japanese actors blacked up as South Pacific natives, then this is the film for you.