>>38528705The Charizard you see in the trailer is owned by a jabroni that runs an illegal underground battling tournament. Prior to the events of the movie, the Charizard lost to the main Pikachu.
The jabroni wants a rematch and Pikachu agrees to it. Jabroni gives his Charizard crazydrugs to make it more powerful and Pikachu, having lost its memory, can't perform any attacks, so basically a crazed Charizard is about to attack Pikachu. Pikachu manages to avoid with help from Tim, as Charizard destroys more and more of the arena.
Eventually Pikachus escape plan is to grab a Magikarp that was knocked out of a fish tank and have it evolve to fight the Charizard. It doesn't just evolve at that time though so that's just a gag. Some more shit happens and the effects of the drugs on the Charizard fade but then the Magikarp DOES evolve, and you see the Charizard whimper as it stares up at this giant Gyarados. Pikachu says something like "Did I tell you I don't float?" and then the Gyarados uses some water attack, flooding the entire room and throwing Tim, Pikachu and the Charizard out of the building.
The Charizard doesn't show up again, however the main villains Ditto does turn into one (as well as Machamp, Lucy, Ms. Norman and Roger) during the climax of the movie to try and stop Tim from foiling their plan. 
