Obvious models of US Air Force jets shoot down mysterious model planes in the Arctic ("Micromachines at 12 o'clock! And G.I. Joe is there."), and the atomic bombs on one of those planes go off on impact and just happen to revive a stupendous tusked turtle frozen in the ice. Gamera, who walks upright most of the time and looks somehow crudely constructed, smashes the obvious model ship of a Japanese scientific expedition ("Abandon toy! Abandon toy!"), and the handful of survivors return to Japan ("The captain has turned off the No Dubbing sign. You are free to speak any langage you choose.") just in time for Gamera to also show up.
A pudgy-cheeked boy named "Kenny," heartbroken over being told to give up his tiny pet turtle "Tibby," happens to be on top of a lighthouse knocked over by Gamera. The giant turtle, though, just happens to take Kenny in his paw and lower him to the ground, and for the rest of the movie Kenny is tagging along with the scientists and military leaders trying to deal with Gamera, telling them that "Gamera loves all children" even as the object of his own affection is wading through Tokyo. A desperate plan involves hitting Gamera with bombs that freeze things for ten minutes and then using that time to plant explosives under him and flip him on his back. ("Pineapple back.") Gamera, though, happens to not only be able to draw his head and limbs inside his shell but to then jet flames from where the limbs go, spinning himself through the air. The second plan involves luring Gamera to the "Z Plan," and despite a typhoon that almost spoils their best efforts Gamera is shut inside the nose cone of a tremendous rocket and blasted off to Mars. (The "bots" gleefully ask "Hey, Joel, remind you of anything?" at that, and even sing some of their own show's theme song.) Kenny looks forward to becoming an astronaut and reuniting with Gamera.
It may be that the episode itself feels a bit slower than that description, but there are fun moments in the "host segments," including Tom Servo singing an ode to Tibby (with Crow in a particularly disbelieving mood), the bots attacking a voodoo doll of Kenny until Joel tells them to be more positive, and Gamera himself flying past the Satellite of Love. In a somehow strange yet fitting development, when Gamera calls from inside his shell to appear on the "Hexfield Viewscreen," he takes off his turtle mask and Mike Nelson in a green turtleneck is talking to the bots, explaining that he's "using Kenny." At the end of the movie, Joel thanks the "mads" for "sending us not such a bad movie this time." (Following right after "Cave Dwellers," the comparison is possible.) Dr. Forrester in response tells Frank to give Joel a "shock to the shammies," and Joel takes this about as badly as you might expect.