Son, Gohan

Gohan warned Goku to never look at a full moon and to stay indoors on nights of one, implying that he had already transformed before and Gohan managed to survive the first time. He followed his advice for sometime until one night when Goku stepped outside to relieve himself; he then glanced at it, transformed into an Oozaru and killed Gohan by stomping on him. From that time on, Goku believed that Gohan's soul was in the Four-Star Dragon Ball.

He is brought back by Uranai Baba during the Fortuneteller Baba Saga to make a point to Goku that he needs to train harder and make his tail work for him instead of against him. He also appears in the filler mini-saga "The Wedding arc" where he is an assistant to Annin and Goku must use the Magical Furnace to put out the fire on Ox King's castle.

He then only appears in flashbacks for the rest of the series. Grandpa Gohan is a playable character in Dragon Ball: Advanced Adventure and Dragon Ball Z: Budokai Tenkaichi 2.