nDs-mPeG, usually abbreviated DPG, is a special format of MPEG-1 video specifically for playback using the homebrew Moonshell program for the Nintendo DS. The video is encoded on a computer and then transferred, along with Moonshell, to the DS for playback.
The movie’s basic premise centers around the existence of a “Reverse World,” a kind of alternate universe designed to correct imbalances in the “Real World.” Five years before the events of this movie, a research scientist named Newton Graceland apparently discovered the Reverse World and its sole resident Pokémon, Giratina, a winged, six-legged, metallic dinosaur-like creature. He then tried to tap Giratina’s power with the help of a young assistant, Zero.
When Newton had a change of heart, Zero broke with him and struck out on his own to try to trap Giratina by using a machine that Newton designed to absorb Giratina’s power so that he, Zero, could gain control of the Reverse World and enter and leave it at will. None of this made much sense to me since there doesn’t seem to be much in the virtually empty Reverse World to want to control and Zero doesn’t seem to have much trouble getting in and out of the real world when he wants to anyway.