The movie starts with the Other World Tournament going on and a match is starting between Goku and Pikkon. The scene changes to the Check-In Station and shows a teenage Ogre guarding the Soul Cleansing Machine, but he is distracted with his heavy metal music. His lack of attention allows the machine to become too full, and, as a result, the machine explodes, releasing all of the evil energy at once. The young ogre is enveloped in the evil smog and is transformed into a giant (seemingly innocent) monster of incredible power named Janemba. Janemba's first order of business is to place a barrier around the Check-in Station of the Other World. This barrier prevents King Yemma from maintaining order between realms. With Yemma trapped, the souls of Other World are free to return to the land of the living. Videl and Gohan are summoned to take care of them.
Bulma and the others gather the Dragon Balls, and summon Shenron. They wish for all the souls to return to the underworld, but Shenron informs them that he can send them back but there is nothing stopping them from coming back, and that something is wrong in Other World.
In the Other World, Goku and Pikkon were fighting in the final of the Other World Tournament, but then are called to go to King Yemma and see what is going on. When they arrive, King Yemma informed them that the monster that did all of this was on the roof of the check-in station. Both Goku and Pikkon are surprised by the tremendous size of Janemba. Goku is excited about his power and lures Janemba to Hell so that Pikkon can start working on the barrier. Once arriving in Hell, Goku is shocked to find it has been changed into a psychedelic, weird world filled with colorful stones. Pikkon attempts to break the barrier, and Goku begins fighting Janemba. Janemba has strange powers that allow him to defy, or rather define, reality (such as creating a portal to punch through that leads right to Goku and forming what seems to be a perfect replica of Goku in his hand, complete with its own Kamehameha), and even as a Super Saiyan 2, Goku is losing. He then powers up to Super Saiyan 3 to defeat the monster.
On Earth, Mr. Satan is winning over the Zombies and happy that they are enemies that he can beat. Frieza arrives shortly after Gohan and Videl get rid of a large group of zombies, and Frieza starts to taunt Gohan. Before they start fighting, Gohan introduces himself with a short speech and dance, saying "I am son of Goku, guardian of all that is good." However, Gohan defeats him with a single punch to the stomach, prompting the rest of the villains to retreat in fear. Afterwards, Gohan does his Justice Pose 1. In the afterlife, Pikkon discovers that cursing at the barrier causes it to break, and the monster, which Goku thought he had defeated, has transformed into a smaller, more powerful form. He makes a sword from an ogre club he finds on the ground (another example of Janemba's power over reality), and starts to easily beat Goku with a swing from his sword, creating a dangerously sharped blade of thin air. He then traps him in a triangular cage made from Blood Pond, and then cuts it down to fit Goku.
Vegeta comes to help Goku. He starts to fight Janemba in his strongest form, Super Saiyan 2, but is no match for him. Goku breaks out of Blood Pond and lands on the ground. Vegeta was thrown into a cage of spikes, but Goku catches him in time and they both take cover into the cage of spikes.
Goku knows they cannot win as separate entities, so he suggests using the fusion technique. Vegeta becomes skeptical, first off that the pose for the Fusion Dance is embarrassing, and furthermore tells him he would rather die than to fuse with a low class Saiyan. But Goku calmly states that Vegeta is already dead. Goku persuades him to agree, and then they try the Fusion Dance. Vegeta agrees, however, he fails to extend his index finger at the last second, and Veku (as named by South Kai) is created. This fighter is weak and can do little but fart on Super Janemba's face and use his "rabbit feet" technique to run away. Right when Janemba is about to destroy him, the fusion runs out and Goku and Vegeta escape. Vegeta curses Goku, saying fusion is useless, but North Kai telepathically points out that it is Vegeta's fault because his index finger was made into a fist and created the blimp Veku. Pikkon then comes after giving up on the barrier around the Check-In Station and begins to fight Janemba to give Goku and Vegeta more time to perform the fusion. Pikkon figures that Janemba is made of the same material as the barrier, and begins cursing at it. Surprisingly, it works, and the creature is caught completely by surprise. However, it is able to incapacitate Pikkon, although those precious few seconds allowed Goku and Vegeta to perform the Fusion Dance, which is successful, forming Gogeta.
On Earth, Goten and Trunks sense their dads fusing, and also fuse to create Gotenks. Gotenks defeats The Dictator's army with the Super Ghost Kamikaze Attack in one shot. Gogeta is formed, and he defeats Janemba with his ultimate attack:the Stardust Breaker. As a result, the teenage ogre returns. Scared by Gogeta, he runs away. Hell is returned to normal and King Yemma is freed with lots work to do. Gogeta defuses, Goku and Vegeta say farewell to each other, and Vegeta returns to his spirit form. Goku and Pikkon return to the Grand Kai's planet. All of the souls are returned to the machine, which is restored.
On Earth, Gohan, Goten, Videl and Trunks are returning home. Goten and Trunks know that it was Goku and Vegeta that saved them, but they refuse to tell anyone. They are chased home by a angry Gohan and a annoy Videl. In the English version, Goten and Trunks were spying on them, and joked about Gohan and Videl kissing which makes them be chased home by a crossed Gohan and an embarrassed Videl. Meanwhile, Shenron remains summoned and asks if anyone still wants to use their wishes, sounding impatient.
- Masako Nozawa as Son Goku, Son Gohan, Son Goten, Gogeta & Gotenks
- Ryo Horikawa as Vegeta & Gogeta
- Takeshi Kusao as Trunks & Gotenks
- the late Daisuke Gori as King Yemma & Mr. Satan
- Hiromi Tsuru as Bulma
- Naoko Watanabe as Chi-Chi
- Yuko Minaguchi as Videl
- Hikaru Midorikawa as Pikkon
- Masaharu Sato as Shenlong
- Joji Yanami as King Kai & the Narrator
- Toku Nishio as South Kai
- Bin Shimada as West Kai & "The Dictator"
- Keiko Yamamoto as East Kai
- Ryuji Saikachi as Old Kai
- Tessho Genda as Janemba
- Kazumi Tanaka as Jeice
- Ryusei Nakao as Frieza
- Sean Schemmel as Goku, King Kai & Gogeta
- Kyle Hebert as Gohan, Pikkon, West Kai & the narrator
- Kara Edwards as Goten, Videl & Gotenks
- Christopher R. Sabat as Vegeta, Gogeta, Shenron, Jeice & "The Dictator"
- Laura Bailey as Trunks & Gotenks
- Chris Rager as Mr. Satan & King Yemma
- Tiffany Vollmer as Bulma
- Cynthia Cranz as Chi-Chi
- Dameon Clarke as South Kai
- Stephanie Nadolny as East Kai
- Evan Jones as Old Kai
- Jim Foronda as Fat Janmeba
- Kent Williams as Skinny Janemba
- Linda Young as Frieza
- The English version of Fusion Reborn is the only Dragon Ball Z film to be rated by the Motion Picture Association of America. It is rated PG for action violence, thematic elements, and rude humor.
- There is a brief Michael Jackson reference in the beginning of the movie, when Saike Demon is dancing he simulates a moonwalk, stands on his tip toes, and grabs himself.
- When Goku and Pikkon are being introduced in the tournament at the beginning of the movie, Goku is referred to as the defending champion, even though in the last Other World Tournament it was a draw due to them both touching the ceiling during the battle. However, during their original battle, Goku was briefly declared the winner of the first tournament before Grand Kai told them touching the ceiling disqualified them.
- In the English version, Shenron offers to grant three wishes rather than the regular two, however in the Japanese version, he says two (one wish was previously used by Bulma to resurrect all the good people killed by Majin Vegeta the day of the 25th World Martial Arts Tournament).
- All swastikas (in the Dictator scenes) are removed from FUNimation's DVD.
- The Dictator's battle against Goten and Trunks was removed when it was aired on Toonami and later Nicktoons.
- The Dictator mentions how Goten and Trunks in their Super Saiyan forms have "blond hair and blue eyes" (even though the eyes are green) referencing Hitler's penchant for the Aryan race.
- When Super Saiyan 3 Goku goes up into the air to blast Super Janemba, Super Gogeta kicking Super Janemba is shown in the background.
- In one scene, one of the Kais refers to Veku as "what an artful dodger" as he had been avoiding Janemba's attacks by running away and farting. This is a reference to the novel Oliver Twist, by Charles Dickens. One of the characters is named the Artful Dodger because he can pick peoples pockets and run quickly.
- In the video game Dragon Ball Z: Buu's Fury, the events of this movie happen after Fortuneteller Baba takes the dead Goku back to the Other World (episode 248) and after Mr. Satan meets Majin Buu (episode 252). This is even though Goku is not seen returning to Grand Kai's planet in the manga/anime after Baba brought him back to the Other World, instead being at the Sacred World of the Kais, either helping Gohan with his Z Sword training or watching the battle on Earth in a Crystal Ball while Old Kai was unlocking Gohan's hidden abilities.
- Extra parts to the movie are added in the story mode of the video game Dragon Ball Z: Budokai Tenkaichi 2: Great Saiyaman and Videl fight 2 vs. 2 battles against Cui and Salza, Bojack and Zangya, Frieza and Cell (Cell did not appear in the movie), and finally Vegeta is allowed to keep his body and has a match against Goku.
- The movie is retold in the PSP fighting game Dragon Ball Z: Shin Budokai, with the story occurring during a time of apparent peace shortly after the battles with Majin Buu.
- Since episode 241 (which is set approximately one day after the tournament), the Z Fighters still on Earth believe Gohan to be dead in the series, while in the movie they interact with him as if this is not the case. The movie occurs 9 days after the tournament, as shown on Videl's watch.
- Dende explicitly stated in episode 240 that the Z Fighters would have to wait four months to use the Dragon Balls again due to Bulma and the others summoning Shenron and wishing for Vegeta's rampage to be undone. Yet, if this movie takes place a few days later, the Z Fighters on Earth should not have been able to summon Shenron.
- The 22nd Shunsuke Kikuchi music package for the franchise starts here. The cues were designated "M20XX" codes, and this package would make its series debut in The Innards of Buu.
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