A lunar eclipse causes a violent moonquake [although how this happens is beyond me, since unlike the Earth, the moon is geologically dead and doesn't have quakes], which releases a hibernating, energized monster that lands on the Earth in the Pacific Ocean. Utilizing his gravitational powers, the moon monster creates a giant whirlpool that imperils the Calico and its crew. Calling on Godzilla, the Big G battles the moon monster and ultimately hurls the creature back into space, where he's recaptured by the moon's gravity (that was one hell of a feat, even for Godzilla!).