Mewtwo Strikes Back(also called "Pokémon the First Moive") was the first movie released in the US. It is currently available on video and DVD. The plot is as follows:
Some scientists (funded by Giovanni, leader of team rocket...) were able to obtain a mew fossil and attempted to make the world's strongest pokémon. They see their creation as an experiment. Mewtwo the pokémon they created doesn't like what they had in store for him. So he blows up the lab. Then Giovanni arrives in a helicopter. He offers Mewtwo the chance to rule the world as equals (Mewtwo accepts). Mewtwo goes through many battles (if you watch the TV show you probably saw Mewtwo beat-up Gary's Kidoking and Arcanine). Then later Giovanni tells Mewtwo that his purpose is to serve humans (bad thing to do). Mewtwo then destroys the base and flys away (you see the building blow-up in the TV show). Next Mewtwo sends out invitations to the strongest trainers claiming the greatest Pokémon Master wants to have battle with them...
If you want to hear/see the rest you will have to see the movie.
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