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]