Riding on the success of Godzilla from a decade earlier, Gammera the Invincible (1966) isn't too bad if you're into the whole "guy in a rubber suit" monster thing. I happen like such things for their campiness, so for what it is, I got what I expected to see in this film.
A Soviet jet is flying in U.S. air space over the arctic and U.S. forces are in hot pursuit.
After several warnings, the U.S. jets shoot down the Soviet one. Unfortunately, it was carrying a bomb and it explodes on impact.
The force generated is enough to wake up Gammera, a giant prehistoric turtle that has been imprisoned in the ice for millions of years.
Gammera is pretty pissed off after being awakened from his long nap, and goes on a rampage. For some reason, Tokyo is his intended destination.
Natives in the area where Gammera originated somehow have knowledge of this creature that is supposed to have been hidden for millions of years, and they hand over a stone tablet that contains secret ancient information.
While passing the surrounding islands, a turtle-obsessed boy encounters the monster. At first Gammera is hostile, but winds up saving the boy instead. This act, in the boys mind, makes them best friends. He spends the rest of his time in the movie trying to reconnect with his "buddy."
Meanwhile, the scientists and authorities are in a panic as to how to contain the situation and stop the monster from continuing his path of destruction. Their first plan, to freeze him and then blow him up with dynamite, backfires. It turns out Gammera can retreat into his shell and convert himself into a sort of flying saucer.
Their second plan... Plan Z, has to work or all is lost...
Gammera the Invincible- movie trailer