It is no secret that Dragon Ball Z fans are not particularly fond of Dragon Ball GT. In the immediate aftermath of the Buu Saga, creator Akira Toriyama swore off making any more Dragon Ball related content, feeling there was no more story to tell. Toei Animation disagreed. So they started up Dragon Ball GT, a show that milked the remainder of the Dragon Ball gold mine for every last coin.
While some people have a fondness for Dragon Ball GT, others don't. Regardless of your opinion of the controversial sequel, however, one thing that cannot be ignored is how Dragon Ball GT forever changed its universe law -- until Dragon Ball Super retconned everything. Still, what were the biggest changes made from Dragon Ball Z to Dragon Ball GT? And what stayed the same?
10 (Same) Another Set of Dragon Balls
One of the most important plot points in Dragon Ball Z is the revelation of another set of Dragon Balls, more powerful than the ones on Earth. It reveals that the earth set, while important, are not unique.
On the other hand, the Black Star Dragon Balls are the key that kick off the plot to Dragon Ball GT. The Black Star Dragon Balls are spread throughout the galaxy. They're a precursor to the more well-known ones used throughout the series. They turn Goku into a child, and, if not gathered together again within a year, will blow up Earth.
Like the prior set, this develops the lore, further expands on the universe, and returns the focus back on collecting the titular Dragon Balls.
9 (Change) A Return to Dragon Ball Style Story-Telling
On the other hand, the returned-focus on Dragon Ball collecting, combined with Goku being a kid, offers a change to the pre-Dragon Ball Z era. This is further compounded by an emphasis on humor and adventure over epic fight scenes.
While the later Baby Saga tries to return to the Dragon Ball Z aesthetic, Dragon Ball GT never feels like it follows in the DBZ style of high-powered action. Whether or not that is a good thing remains up to the viewer.
8 (Change) Only Goku Matters
While Goku was always the main protagonist, Dragon Ball Z always presented every character as incredibly powerful. There are huge stretches of the series where Goku is either incapacitated, traveling, in another dimension, or dead. During this time, the other characters take priority. In fact, Goku never actually lands the final blow on any of the final villains. Though Kid Buu seems like an exception, he only won by channeling the collective energy of Earth into a Spirit Bomb.
On the other hand, every major fight in Dragon Ball GT is started and finished by Goku. When other characters fight, it's only so they can be beaten to validate how powerful the enemy is before Goku wins. It results in a strange sense of irritation, as nothing really matters until Goku steps in to handle the situation himself.
7 (Change) Trunks Works at Capsule Corp
Trunks is either a child or time traveler throughout Dragon Ball Z, so the idea of him working a job seems a little surreal. Nevertheless, in Dragon Ball GT, Trunks becomes a member of his mother's company at Capsule Corp.
This ties in with him working with Goku throughout Dragon Ball GT, as he is tied up with the company lending Goku a space ship. While the time traveling Trunks from the Android and later Goku Black arc is more popular, it is interesting to see another side to this half-Saiyan.
6 (Same) Planet Vegeta Didn't Originally Belong to the Saiyans
The introduction of Baby is often regarded as the point where Dragon Ball GT gets good. The idea of an alien race getting revenge on the Saiyans is interesting. It brings the conflict back to the era of Dragon Ball Z where Saiyan history informed the plot.
However, while the idea of the Tuffles being over-run by the Saiyans sounds like an idea original to Dragon Ball GT, it's actually older than you think. In the Dragon Ball Z OVA The Plan to Eradicate the Saiyans and its remake of the same name, a mad Tuffle scientist -- the last survivor of his kind -- creates a Tuffle bio-android fueled by sheer hate named Hatchiyack. In many ways, Baby is remarkably similar, being created as the last Tuffle, exacting revenge by creating a new Planet Vegeta in his image. And by...eradicating the Saiyans.
5 (Change) Inconsistent Power Levels
Dragon Ball GT's biggest flaw is inconsistency. Power levels and transformations mean virtually nothing. Transformations make no sense in terms of power-scaling. Super Saiyan transformations feel cheap and unimportant.
But this is most apparent whenever Kid Goku appears. Kid Goku, except when the plot requires it, can take just as much punishment as his Super Saiyan 4 counterpart and then some, yet remain unharmed. Most notably is the end of the series when Omega Shenron barrages Kid Goku with energy blasts that would have blown his Super Saiyan 4 counterpart to pieces, yet he remains unharmed.
4 (Change) Few Saga-Long Villains
Dragon Ball Z is often divided into several sagas, where the main plot centered around defeating a particular adversary, usually with a smaller saga preceding it. Saiyans to Frieza, Androids to Cell, and Babidi to Majin Buu, the saga structure gave Dragon Ball Z a sense of continuity throughout.
Dragon Ball GT only has one villain who remains the main antagonist for more than a few episodes: Baby. The rest of the arcs are guided more by scenarios than actual singular villains. Gather the Black Star Dragon Balls. Close up Hell. Fix the Dragon Balls. There are central villains, yes, but not in the same way that Saga Villains existed in Z.
3 (Change) The Dragon Balls' Negative Energy
Perhaps the most interesting addition to Dragon Ball lore is Negative Energy. The heroes used Dragon Balls without consequence in the original series. Any problem? Wish it away. But Dragon Ball GT revealed that, for every wish, they filled the Dragon Balls with too much negativity. Which resulted in the birth of the Shadow Dragons.
The Shadow Dragon arc established a sense of finality to the DBZ saga, as, at long last, the characters' own deeds came back to haunt them. The Dragon Balls were no longer safe.
2 (Same) Dr. Gero and Pilaf Ruin Everything
There is no one villain who appears throughout every Dragon Ball series to wreak havoc. However, the closest two antagonists that spurred on the worst nonsense throughout Goku's entire life are Emperor Pilaf and Dr. Gero. Pilaf is the very first villain Goku faced as a child. He later released Piccolo starting the events that culminated in the Piccolo Saga. However, in Dragon Ball GT, Pilaf returns again, collecting the Black Star Dragon Balls and triggering the entire grand tour across the universe.
However, if possible, Gero is even worse. Head scientist of Dragon Ball's Red Ribbon Army and creator of the Androids (and Cell), Dr. Gero dreamed of murdering Goku for decades. This desire didn't stop after death, as Gero's plot opens a gate to Hell in order to drag Goku into Hell. This results in Goku, hoping to undo the damage Gero and his Super 17 left behind, turning to the Dragon Balls, which overloads them with Negative Energy...
1 (Change) Goku Never Returns
This is arguably the most fascinating change. Goku leaves a lot in Dragon Ball. He leaves to train with Kami. Leaves to train with King Kai. Leaves to travel the Earth back from Namek. Dies. Trains with Uub. Goku is always leaving, but he always returns.
On the other hand, at the end of Dragon Ball GT, Goku goes away...and doesn't really ever come back. He fuses with Shenron and the Dragon Balls, disappearing for good. Sure, he returns 100 years later, but the world has moved on from him. No one, save for Pan, remembers he even exists. There is a sense of finality to the end of Dragon Ball GT, that this is it. Arguably, the final episode is the highlight of the entire series. It truly feels like the end of a saga.