One of the earliest known concepts for Godzilla's 21st outing, Godzilla vs. Astrogodzilla would have been a far cry tonally compared to previous entries in the Heisei VS series. While not much is known about how far along in development this concept went, many elements would eventually be carried over to the final product of Godzilla vs. SpaceGodzilla (1994).
The primary antagonist, Astrogodzilla, would be heavily revised as time went on. Starting off as essentially a proto-SpaceGodzilla, Astrogodzilla would have followed more of an ice motif, and its body would have been pure white. Likewise, its origins would have been much more cut and dry, compared to SpaceGodzilla who had multiple theories surrounding its creation. However, as newer drafts of the movie were created, the ice motif would eventually be replaced with the idea of a "crystal organism", and the concept of Astrogodzilla would eventually evolve into SpaceGodzilla.
Supporting cast would have consisted of reoccuring actress Megumi Odaka as Miki Saegusa, as well as Little Godzilla, the new anti-Godzilla weapon Moguera, and surprisingly Mothra, who would have returned to Earth after her trip to outer space as shown in the ending of Godzilla vs. Mothra (1992).