From the ever-reliable YouTubes…1969’s Gamera vs. Guiron is described thusly:
Aliens kidnap two children and take them to another planet for the purpose of getting knowledge from their brains, but Gamera follows and tries to rescue them.
Spit-take Alert! Giant Turtle acrobatics at the 1:04:15 mark!
…or…watch the Mystery Science Theater 3000 version: