From Dragon Ball Encyclopedia, the ''Dragon Ball'' wiki
Gyumao (牛魔王, Gyūmaō; FUNimation "Ox-King", Viz "Gyū Maō") is the king of Fire Mountain and the father of Son Goku's wife, Son Chichi. He once trained with Goku's adoptive grandfather, Grandpa Son Gohan, under Muten Roshi.
 Creation and concept
He is based on Niúmówáng ("Ox-Demon-King", "Ox Devil Lord" or "Ox Tyrant"), a character from the Chinese novel Journey to the West, from which the Dragon Ball series is based on. In the novel, the character befriended the Monkey King (the equivalent of Goku). His wife was also the owner of the trademark Bansho Fan.
Ox-King is quite large, and has a lot of facial hair. His appearance is one of the most changing of all the supporting characters in the series. When he first appears, he is drawn more barbaric and menacing, and wields an axe. By the end of Dragon Ball and beginning of Dragon Ball Z, he dresses in normal attire and wears glasses instead of goggles. His facial hair is more detailed. In Future Trunks' timeline, he appears the same except now sporting gray hair and a new outfit. In the Kid Buu Saga, he appears to be much bigger, his facial hair grows out more, and the hair in the back of his head extends out a little over his shoulders. There are also slight alterations to his clothes. At the end of Dragon Ball Z, his hair is gray and he wears formal clothes with an orange tie. In his very first appearance in GT, his tie is purple, and in his next appearance, it is yellow. Overall, Ox-King's character design changes more than any of the other supporting characters such as Puar, Oolong, Yajirobe, Dr. Briefs, etc.
Despite his threatening sounding name, Ox-King is really quite harmless and fun loving. He was somewhat demonic when his castle became engulfed in flames on Fire Mountain during a picnic with his daughter, and wreaked havoc through the village at the foot of the mountain. In the anime, he has a few large roles though from time to time, mainly involving keeping his daughter out of trouble.
 Dragon Ball
 Emperor Pilaf Saga
Living on Fire Mountain, Ox-King would either scare or eat anything that came along, due to the fact that his castle was stuck up on the mountain in eternal flames. This leads residents in the surrounding area to dub him "The Emperor of Demons". Bulma, Goku, and Oolong stumble upon him and Chichi during their quest for the Dragon Balls. They agree to help him, and Goku along with Chichi (whom he has to find first) brings back Master Roshi, the only one strong enough to break the barrier. Master Roshi fires a large Kamehameha at the wall of fire, and destroys it. However, the Kamehameha is so big that it takes the entire mountain with it. After Master Roshi blew the mountain and castle away, Gyumao promised to not hurt anyone again. Although his castle is gone, Gyumao and Chichi shrug it off and vow to build a new one. After Goku finds Chichi, who had been missing, and returns her to her father, Gyumao offers her to Goku as a wife in gratitude of her safe return. Not knowing what a wife is, Goku agrees.
 King Piccolo Saga
Four years later Gyumao and Chichi reappear in the anime filler, where they are seen watching King Piccolo on TV. Later, while on his way to the king's castle, Goku spots some of King Furry's guards attempting to kill Gyumao on King Piccolo's orders to kill all well-known martial artists, him being the first on the list. Goku puts a stop to it and heads off to stop King Piccolo. Later on they are seen outside, watching the celebration fireworks after King Piccolo is killed.
 Piccolo Jr. Saga
Again in the anime filler, three years later, Chichi returns to Gyumao's castle with Goku. Chichi announces she and Goku are getting married, which surprises Gyumao since he thought she was just going to tell him what the Tournament was like. Gyumao is eventually trapped in his own castle after they are once again engulfed in flames, and he vows to protect Chichi's wedding dress from the flames. Goku and Chichi first go to find the Bansho Fan to help put the flames out but they did not succeed in stopping the flames. Baba then told them about the Furnace of Eight Divisions, a part of the Other World which was the cause of the flames. Goku and Chichi manage to repair the holes in the Furnace, which narrowly saves Gyumao. Sometime over the three years between the King Piccolo Saga and Piccolo Jr. Saga, Gyumao seemingly gave up being a warrior and also abandoned his old armor towards the end of Dragon Ball for the look he would have for most of Dragon Ball Z. Gyumao also becomes noticeably friendlier during this time.
 Dragon Ball Z
In Dragon Ball Z, he appears in the anime more frequently throughout the sagas, usually seen at home trying to calm Chichi down and keep her from rescuing Gohan from situations that could kill her.
 Battle against Cell
Ox King watches the battle against Cell on TV at Chichi's house. When the TV breaks, Baba comes to the house and they watch the fight on Baba's Crystal Ball. Later, Gohan comes home telling that Goku died, making Chichi break down in tears.
 Goku's return
Seven years after the defeat of Cell, Ox King has another grandson named Goten, who was born shortly after the Cell Games Saga. When Goku is to return to earth for one day, Ox King attends the 25th World Martial Arts Tournament to cheer on his family and friends.
 The monster Majin Boo, death, and revival
When Vegeta kills a massive number of people at the World Tournament stadium to get Goku to fight him, Ox-King goes with the group to gather the Dragon Balls. Ox-King takes refuge at Kami's Lookout, where he and the others learn of the monster Majin Buu and the deaths of Vegeta and Gohan (the latter of whom was actually with Supreme Kai and Kibito on their planet). Hearing the tragic news makes Chi-Chi faint. Ox-King keeps watch over her until she recovers. A day later, Super Buu finds the tower and allows them to live for a short time. Ox-King attempts to keep Chi-Chi away from fighting Buu, but fails when she is turned to an egg and smashed. Ox-King is then one of the characters who accompany Krillin and Dende when they decide to follow Buu and Piccolo to the hyperbolic time chamber. When Super Buu escapes from the Hyperbolic Time Chamber after Piccolo destroys the door, he turns Ox-King and the rest of the group into chocolate and eats them, killing them instantly. Later the destroyed Earth and all its people are revived and give some of their energy to help Goku make the Spirit Bomb to destroy Kid Buu.
 Ten years later
 Dragon Ball GT
In Dragon Ball GT, the Ox-King no longer appeared to visit Goku's family as regularly as he did before or maintain his role of calming Chichi down, which is now done mostly by Videl. He only makes cameo appearances in "Collapse from Within" and "Piccolo's Decision". From the 4th GT ending credits, Ox-King appears to be the tallest character; even taller than Piccolo and Majin Boo. He also appears in one of the final flashbacks where Bulma, Oolong and Goku first met Ox-King.
 Alternate timeline
Main article: Future Gyumao
Ox-King was one of the few characters to survive in Future Trunks' timeline as seen in The History of Trunks. He was seen still living with Chichi and followed what little news of Gohan reached them. Because he was shown to be living with Chichi, it is likely his kingdom fell victim to Future Android 17's and Future Android 18's rampage around Earth where most civilizations were attacked, though it is unknown how he survived their attack.
Gyumao appeared in Dragon Ball Z: Dead Zone.
Gyumao appeared in Dragon Ball Z: Fusion Reborn.
Gyumao appeared in Dragon Ball Z: The History of Trunks.
Gyumao appeared in Dragon Ball Z: Battle of Gods.
 Video games
Gyumao appeared in Dragon Ball: Advanced Adventure.
Gyumao appeared in Dragon Ball Z: Buu's Fury.
 Voice actors
- Japanese dub: Daisuke Gori; Ryūzaburō Ōtomo
- Blue Water dub: Dave Pettitt
- Ocean Group dub: Dave Ward
- FUNimation dub: Mark Britten (DBZ Season 3-6, The History of Trunks); Kyle Hebert (DB, DBZ Season 7-9, DBZ Remastered Season 1-3, DBGT, Remastered DBZ Movie 1 & 2); Christopher Sabat (DBZ Movie 1 & 2)
- Though Ox King's age is never revealed, it can be assumed that he is in his early sixties by the time the Buu saga arrives. His hair is naturally orangish-brown when he first appears, but gradually gets darker as the series progresses to the point of being black up until the end of Dragon Ball Z where it finally starts to gray. By the time Dragon Ball GT begins, he is supposedly over 80 years old and still living, shown by his minor appearances in some episodes.
- It was Ox King's idea to name Goku and Chichi's first child Gohan. Although Gohan cried at his earlier name ideas, he was happy when he got his real name.
- Though generally very polite and generally disinterested in girls, Ox King is shown to have a perverted side similar to Roshi's when watching Maron sunbathe in "Krillin's Proposal".
- Ox King's height keeps changing constantly. One example would be when they summoned Shen Long during the Buu Saga, in some scenes it shows everyone up to his stomach, but in others they only seem to be as big as his knee.
- Ox King originally wanted to name Gohan "Ox King Jr.", "Ox in the Box", and a long list of other names with the word "Ox" in them.