Richard Donner confirmed that he had been interested in writing at least two more Superman films which he intended Tom Mankiewicz to direct, and use Brainiac as the villain of the third film. Donner departed the series during the production of Superman II. The film was announced at the 33rd Cannes Film Festival in May 1980. In December 1980, producer Ilya Salkind wrote a treatment for this film that included Brainiac, Mister Mxyzptlk and Supergirl. The treatment was released online in 2007. The Mister Mxyzptlk portrayed in the outline varies from his comic counterpart as he uses his abilities to cause chaos. Dudley Moore was the first choice to play the role. In the treatment, Brainiac was from Colu and had discovered Supergirl in the same way that Superman was found by Jonathan and Martha Kent. Brainiac is portrayed as a surrogate father to Supergirl and eventually fell in love with his "daughter" who did not reciprocate his feelings, as she had fallen in love with Superman. Brainiac retaliates by using a personality machine to corrupt and manipulate Superman. The climax of the film would have seen Superman, Supergirl, Jimmy Olsen, Lana Lang and Brainiac time travel to the Middle Ages for a final battle against Brainiac. After defeating him and leaving Brainiac behind, Superman and Supergirl would have married at the end of Superman III or in Superman IV. The treatment was rejected as being too complex and expensive to shoot. Because of the high budgets required for the series, the Salkinds considered selling the rights to the series to Dino De Laurentiis. The significance of computers, the corruption of Superman, and the splitting of Superman into good and evil would be used in the final film. The film was originally intended to be titled Superman vs. Superman, but was retitled after the producers of Kramer vs. Kramer threatened a lawsuit.