Dragon Ball Z: Atsumare! Gokuu World

This anime was released exclusively as VHS with the "Terebikko's videogame".

Dragon Ball Z: Atsumare!

Gokuu World tells a feature-length story involving time travel leading up to the group's first encounter with Cell (portrayed slightly differently than in the mainstream series).

The plot of the animation seems as though it could be worked into the mainstream series, particularly in the ten days prior to the beginning of the Cell Games.

However, in this special, Gohan as a kid actually meets Cell, instead of being a teenager after having trained with Goku in the Hyperbolic Time Chamber.