In the original Japanese trailer, most of the scenes were fully animated, yet not used in the final cut. Some of the shots were Ash standing on top of a crystal pillar, as the camera pans around him and he is searching for something, a bunch of random wild Pokémon running away from the crystallization, and a shot of Mewtwo standing at the entrance of a cave with lightning cracking behind it. Supposedly, the 3rd and 4th movies were to inter-connect, with Mewtwo being the one who connects them. Perhaps the anime producers decided to throw that away and instead advertise the then-new Pokémon Crystal game? After all, several elements from the game (the Unown, Suicune, Celebi) appeared in both movies.
