As a child of the seventies, I grew up watching Batman reruns and Godzilla Saturday matinees on television, but even with my fervent imagination I never dreamed of a crossover between the two. The studios that held the rights to the characters, on the other hand, considered that very thing back before I was even born, each of them envisioning the combo as a sequel to their own successful sixties-era movies.
Toho Studios, following the financial success of 1962's King Kong vs. Godzilla, was eager to pit their giant radioactive dinosaur against another American icon, and set their sights on the Caped Crusader. So in 1965, Godzilla series screenwriter Shinichi Sekizawa wrote a proposal for Batman vs. Godzilla.