Fan Casting Superman III (1983)

Another Kryptonian named Supergirl and her dog Krypto have flown to Earth to warn Superman and the world of the extra-terrestrial overlord, Brainiac! Brainiac manipulates Superman into a corrupted version of him as he threatens the world too! Supergirl with the help of Lois Lane, Krypto, and a warped trickster Mister Mxyzptlk must revert Superman back to normal. The final climax between Superman, Supergirl, and Krypto against Brainiac takes place in the Middle Ages.