Godzilla vs. Megalon(ゴジラ対メガロ)

In his 13th film, Godzilla takes a supporting role to the far more prominently featured Jet Jaguar, an Ultra-Man like robot. Aliens take control of Earth's monsters and begin using them to destroy the human race. Jet Jaguar decides to stop the attack by recruiting Godzilla and enlarging himself to Monster-size.