Before Mewtwo Struck Back:
Promotional Trailers & Anime Tie Ins
I must thank Lumina Sumnor for first drawing my attention to the original Japanese trailer for Mewtwo Strikes Back, but I unfortunately know very little about it; I still have no idea when, where, or how it was aired.
The teaser trailers for the Japanese Pokémon movies often have very little to do with the actual movie, and watching this one, I suppose the trailer for the first Pokémon movie set that trend right away! There is some interesting discussion on Dogasu's Backpack as to why this trailer is so weird and what its history might be here.
Despite the mystery and weirdness, I can describe my impressions and share my thoughts about this trailer.
Most of the trailer shows Boijer (the harbor manager), Misty (who appears perhaps older than her usual anime appearance), and a little girl (who looks like a young Nurse Joy, and may represent an average Pokémon fan) sitting happily in the grass finding Pokémon shapes in the clouds.
Then Ash and Pikachu are shown running away from a blast of fire, and then plunging into fast-moving water. There's also Misty, Brock, and Psyduck running frantically though some sort of crumbling purple canyon. These scenes of distress contrast oddly with the happy music that continues to play in the background. Actually, it is downright unsettling.
Mew is not shown in the trailer at all, and Mewtwo is only shown for about a second, half-concealed by shadow in front of some science equipment. Mewtwo's design here seems a little different from what the anime went with in the end. The differences include, most notably and definitively, that his pupil was circular, rather than the final shape, which is more oblong. It's a bit hard to tell with all the shadows, but I think also his face was more round, and his nose seems to maybe jut out a bit more than the final design.
Overall, it is very strange to watch the trailer in retrospect. I wonder what the movie of these ideas would have ended up being like.
There apparently was another Japanese trailer that I can only assume aired later; it includes actual scenes from Mewtwo Strikes Back and also Pikachu's Vacation. One of the scenes included is the shot of Ash and his friends all falling into the fast-moving water, maybe to echo the earlier idea that was in the initial teaser trailer. Also, multiple scenes with Mew are in this trailer, so I guess by now, no effort was being made to keep Mew a secret, heh.
One of the most interesting aspects of this trailer is the glimpse it provides of what I presume is a very early version of the final movie. Not only does it not have the heavily-criticized computer-generated effects (such as the CG clouds) that were later edited into the home release version of the movie, the shot with Mew flitting across the moon seems very different than even the theatrical version: the moon in this trailer is yellow and heavily cratered, the theatrical version has a silver and less heavily cratered moon, and the home release versions have a more photo-realistic take on the moon. How many times did they redraw this moon anyway?
In contrast to the Japanese trailers, the English trailer is instead a call to all Pokémon trainers to take part in the showdown between the two most powerful Pokémon of all: #150 and #151. It consists mostly of stock official art and reveals next to nothing about the actual movie, but is somehow still more informative than the first Japanese trailer.
In addition to trailers, during the lead-up to The First Movie, Mewtwo was also shown as a character in the regular anime itself in order to stir up interest. In the three episodes in which he appears, Mewtwo is under the control of Giovanni, his identity hidden by armor, wires, and shadow. A few scenes from these anime appearances are shown in the movie itself, such as when Gary faces Giovanni and his Pokémon are swiftly defeated by Mewtwo's psychic powers.