4x19 - Dragon Ball Z: Dragon Box

Knowing that it will not change their present situation, Trunks and Kuririn head off to eliminate Cell, who has just been born, for the sake of the future. They discover the larval form of Cell in Doctor Gero's laboratory, and destroy it along with the entire building. While there in the lab, they obtain the design schematics for No. 17, and Bulma begins to look for a weakness in the Artificial Humans.