Kyojin no Hoshi tai Tetsuwan Atom

Star of the Giants vs Astro Boy is an anime crossover special that aired on September 6th, 1969. Broadcasted by the TV Network Nippon Television, it was a collaboration between the studios Tokyo Movie and Mushi Pro in which rival characters on the same network would battle each other over a game of baseball. It’s considered one of the oldest anime crossover specials, but despite its historical significance, only small clips have surfaced over time. (Source: Lost Media Wiki)