The "Lost Movie" started out as a videogame for the (highly unsuccesful) PlayDia videogame console in Japan, The Plan To Destroy The Saiya-Jin, which was a game using animation made especially for the game where the player made choices at the correct times to advance the story. Later, the animation from the game was made into a two-part movie and released on VHS, which is the "Lost Movie".
The story revolves around our heroes battling the evil Dr Raichi, who has placed machines on Earth that produce a gas called Destron, which eradicates all life and negates the Z Fighters ki attacks. After destroying the Destron Gas machines, the gang must travel to the Dark Planet where Dr Raichi and his ultimate creation, Hatchyak, await them.
While the story is nothing special, and the action is a bit bland at times, it is worth watching for the spectacular final battle alone.
its weird, from what ive seen, theres this dude who managed to make "ghost forms" of frieza, cooler, the random saiyan from "tree of might", and a couple of other bad guys. its set during the cell saga, as gohan can go SSJ but not SSJ2.
also, theres devices which stop people using Ki-Attacks, its all pretty weird.