Bagan is a daikaiju that was going to be given a chance to battle Mothra and Godzilla, but was cut out. It is the most popular of the unmade Toho Daikaiju due to its appearance as a final opponent in the Super Nintendo video game, Super Godzilla.
First, Bagan appeared in the original draft of The Return of Godzilla (1984) as a strange shape shifting creature with three forms: dragon, sea monster, and a giant ape. He could change from one form to another and when he did, he recovered from all the injuries done to its previous form. In the end, Bagan would combine into a single monster with the wings, arms and head of the dragon, the chest, arms, and head of the ape, and the legs, eyes, and mouth of the sea monster. He was stronger in this form, but it could not recover from his injuries, thus in this state Godzilla could defeat it. Bagan was cut from the film because Tomoyuki Tanaka did not have the budget for these special effects.
In 1990's, Bagan's body design was completely changed. He became a large three-horned dragon-like kaiju with white, red, and black scales, wings, and a whip-like tail.
In 1990, he was going to have a chance to battle Mothra in Mothra vs Bagan. He would appear as a Yamato dragon beast that lived in Ancient China. His body eventually became frozen in a block of ice in the Himalayan Mountains. Someone frees Bagan by using explosives on the mountain. He starts to wreak havoc and is unstoppabable until Mothra defeats him and saves the world. The film went very far in the development, but it was canceled because Toho decided not to try to create a new Kaiju film without Godzilla after Godzilla vs Biollante (1989) failed at the box office and Bagan was taken out.
In 1993, Bagan appeared as a final enemy in the Super Nintendo video game, Super Godzilla. When Godzilla fights Bagan, he would change into a second stronger form called Super Godzilla and defeat Bagan.
In 1995, another film that starred Bagan called Godzilla vs. Bagan was going to be released and also, Godzilla changes into Super Godzilla in the film and defeats Bagan. But Bagan was taken out and replaced by Destoroyah and the storyline was renewed. The movie was changed to Godzilla vs Destoroyah and it became one of the most successful Godzilla films.