Future Androids 17 and 18 → Future Dr. Gero
It is reported that, in the future, Dr. Gero was killed by the androids he created. The initial designation of Androids 19 and 20 is presented alongside the later explanation identifying them as Androids 17 and 18, and this event is kept separate from Gero’s death in the present. The individual lethal attacker is not identified.
SourceChapter 335 — A Message of Terror (Japanese: 恐怖のメッセージ)Full Color Androids and Cell Arc, Vol. 1 · Akira Toriyama / Shueisha
Additional sourceChapter 348 — To the Laboratory...!! (Japanese: 研究所へ…!!)Full Color Androids and Cell Arc, Vol. 2 · Akira Toriyama / Shueisha
Additional sourceChapter 358 — An Evil Premonition (Japanese: 邪悪な予感)Full Color Androids and Cell Arc, Vol. 3 · Akira Toriyama / Shueisha