"The hat with the four-star Dragon Ball that Gohan wore when he was a kid."
Gohan's Hat first appears at the beginning of Dragon Ball Z where it is worn by Gohan. In the anime, Gohan is wearing it when he loses it to a Sabertooth Cat he encounters in the forest. As his father had given him the hat, Gohan chases after the cat crying; though the Sabertooth Cat manages to elude Gohan. Goku soon encounters the Cat wearing the hat and asks it where Gohan is. The cat replies by growling at Goku, leading Goku to ask it again in a more angry tone. This scares the cat, causing it to drop the hat and flee. Goku later returns the hat to Gohan after finding him and the two leave to go visit Goku's friends at Kame House. After introducing Gohan to his friends, Bulma notices the Dragon Ball on Gohan's hat and Goku explains that he found the 4-Star Dragon Ball which was a treasured keepsake he kept in memory of his grandfather who was his son's namesake, so Goku decided to attach it to the hat and gave it to his son.
The hat played an important role when Gohan was kidnapped by Raditz, as Goku realized he could use the Dragon Radar to track the Dragon Ball on Gohan's hat allowing him to locate where Raditz had taken Gohan. Joining forces with Piccolo, Goku used the Dragon Radar to find the impact site of Raditz's Attack Ball where Gohan was imprisoned, leading to the battle with Raditz. The hat was knocked off of Gohan's head when the raging Gohan broke the Attack Ball, landing outside of the Attack Ball's impact crater, later to be found by Krillin. The Dragon Ball was later removed so it could be used with the other six Dragon Balls to summon Shenron in order to wish Goku back to life after his training with King Kai. The hat does not appear in the manga after this. In the anime it only appears in flashbacks and photographs.
In Dragon Ball Z: Dead Zone, Gohan wears the hat but gets kidnapped by Garlic Jr.'s henchmen for the ball. The Dragon Ball is later removed and used with the other six Dragon Balls when Garlic Jr. summons Shenron to wish for immortality, though fortunately Goku is able to use the Dragon Radar to find Garlic Jr.'s castle before the Dragon Balls scatter.
In Dragon Ball Z: Lord Slug, Gohan wears that hat while hanging out with Piccolo and Icarus at the beginning of the film and when he confronts Lord Slug's soldiers though it is eventually knocked off during the fight and is found by Lord Slug who being a Namekian recognizes it as a Dragon Ball. Slug removes the Dragon Ball and reads Bulma's mind learning about the Dragon Radar which his henchmen use to find the other Dragon Balls so Lord Slug can wish to have his youth restored by Shenron.
Video Game Appearances
In Dragon Ball Xenoverse, Gohan's hat appears as part of one of Kid Gohan's unlockable alternate costume skillsets.
The hat was named Four-Star Dragon Ball Hat in Dragon Ball Xenoverse 2 where it once again appears as part of Kid Gohan's Qipao alternate costume skillset and as an obtainable accessory for the Future Warrior.
- Dragon Ball Xenoverse 2, 2016