Throughout the time of Dragon Ball, Akira Toriyama has left fans wondering and many have even presented their theories and what-if scenarios as to how the characters, storyline, and relations correlate and harmonize with the conditions they are dealing with.
Fans have watched many episodes repeatedly and frame by frame as well to gain in-depth knowledge about the current events taking place in the series and have come up with their own analysis to give insight and confirm, to a certain extent, the lore surrounding the franchise.
10 Using Kaioken with Super Saiyan would have killed Goku
Since the Saiyan Saga, Goku has added plenty of abilities to his arsenal, one of which is his go-to power-up ability, the Kaioken. Fans were expecting that after Goku achieved the transformation of the Legendary Super Saiyan, he would combine it with the Kaioken ability to boost his attributes further. However, in Dragon Ball Super, it is revealed that Super Saiyan already taxed Goku's body and so, using Kaioken would break it apart. Super Saiyan Blue is an exception as it is perfect ki control, like how Goku's body slimmed down when he first achieved God Ki, and doesn’t strain his body, only his stamina.
9 Frieza is Naturally Strong
Frieza was already quite powerful and he didn’t even need to put in the effort. In the Frieza Saga on Planet Namek, Frieza had a whole army at his disposal to do his bidding and always remained in his most basic form. After his return in Dragon Ball Super, it is shown that Frieza, who is determined to get his revenge, begins to train of his own free will. The loss on Namek gave him an epiphany about his lack of strength and drove him to achieve his Golden form that rivaled Super Saiyan Blue and even overpowered it by a slight amount.
8 Master Roshi is the Strongest Human
It was debated whether Krillin is the stronger character, but the Tournament of Power proved this otherwise. While Krillin did eliminate some competitors, he was still the first person to be eliminated from Universe 7's roster, whereas Master Roshi survived through the eighty-man battle royale for a significant duration and even eliminated some of the most powerful and formidable adversaries who would have provided a substantial amount of competition.
Roshi pushed himself to the point where over using the Mafuba technique caused him to have a heart attack and even after being defibrillated, began to fight in the royale.
7 Goku Black's True Identity
After it was revealed that the villain responsible for destroying Future Trunk's home, is Goku, or at least someone resembling him, fans began to speculate and theorize that someone must have stolen the Goku of an alternate timeline and either brainwashed him or hijacked his body/conscience to use to their advantage. This was confirmed when Zamasu reveals how he used the Earth Dragon Balls to switch his body with Goku's and then traveled to another timeline and formed a coup to with the Zamasu there, to eliminate the humans, and had his alternate timeline version use the Super Dragon Balls to become immortal.
6 Android 16 is modeled after Dr. Gero's son
Fans already theorized that Android 16 pacifist nature was odd, being a machine designed to destroy. Then the release of Dragon Ball FighterZ shined more light on this matter when a mother-son relationship was revealed between Android 21 and Android 16. Akira Toriyama also confirmed that Dr. Gero did indeed have a son in the Red Ribbon army who met an unfortunate end and was then used as the inspiration for 16's template. It also confirmed why he kept him decommissioned as he could not bear to lose his son a second time.
5 Super Saiyan isn’t a rage catalyst
Since the first appearance of the Super Saiyan transformation during the Frieza Saga, fans were led to believe that an extreme emotional loss would cause a rage inducing fit that would transform the person into the Legendary form. However, a theory made its way into the lore, that Super Saiyan is not about getting angry, but about proper ki output.
Universe 6's Cabba later proves this theory when teaching Kaulifla and Kale to transform by focusing their energy at a point in their body, noticeably a tingling sensation in the back, and then letting it explode.
4 Potara Fusion is only Permanent for Kais
Old Kai had stated, during the Buu Saga, that once a fusion had been done using the Potara Earrings it would be permanent and the individuals would not split back. However, when Vegito defused inside Buu after lowering his energy barrier, some fans thought that there might be a misconception in the Old kai's statement and speculation circled the franchise that only when a Kai is involved, the fusion will be permanent. Gowasu later reveals in super after Goku himself addresses the ambiguity, that only if a Kaioshin is involved, will the fusion remain permanent and otherwise will dissipate in one hour.
3 Goku and Frieza's fight on Namek is in Slow motion
After blasting the planet Namek's core and making it unstable, Frieza states that the planet will explode in a mere five minutes. He remains confident due to the fact that he is aware that Saiyans can’t breathe in space and so, Goku will eventually suffocate and die even if he was able to get clear of the blast radius of the explosion.
The fight lasts for nine episodes which contradict with the amount of time the planet was supposed to explode in and so, fan theorized that the battle was shown to us in Slow motion while in real-time, it lasted less than five minutes. This theory was confirmed later on by Toriyama himself.
2 The Potential to turn Super Saiyan is Genetic
The legendary transformation was thought to be a great feat and was achieved by both Goku and Vegeta during a traumatic rage-filled episode. Fans, however, theorized that the transformation has a biological link, because if that was all it took to achieve the form then it would be too easy for any Saiyan. Akira Toriyama later revealed a concept of “S-Cells", which were a genetic trait of Saiyan and every Saiyan had the potential to achieve the form by the number of s-cells present in his genetic makeup. This is further backed up by the fact that half-Saiyans achieved the transformation very easily and bypassed the trauma.
1 Vegito would fight Zamasu
During the “Future” Trunks Saga, Goku and Vegeta travel To Ronto’s timeline to put an end to Zamasu. However, Zamasu is able to retain the upper hand in every battle and eventually becomes exponentially stronger when he uses the Potara Fusion to become one being. Fans speculated that a similar situation was when Buu absorbed Gohan, Gotenks and Piccolo and overpowered both Super Saiyan 2 Goku and Vegeta, which led to Vegito's debut. The same speculation arose with Fused Zamasu and everyone believed that Vegito would make another appearance in the series, this time, sporting the new Super Saiyan Blue look.