Fans always explain away why only Goku can voluntarily transform into Super Saiyan 4 in Dragon Ball GT by saying it’s “because it’s Goku,” but Dragon Ball actually solved this mystery long before he even unlocked the first Super Saiyan form.
In chapter 151 of Dragon Ball by mangaka Akira Toriyama, Goku drinks the Super Water of the Gods to unlock his true potential at Korin’s Tower. As he’s ingesting the water, Goku’s face is juxtaposed against an image of the Great Ape, and, immediately afterward, Korin says that he just caught a glimpse of Goku’s true power. Later when battling the Demon King Piccolo, Goku performs a punch that’s clearly associated with the power of the Great Ape.
A Tail Isn’t Necessary to Transform into Super Saiyan 4
In Dragon Ball GT, Super Saiyan 4 can only be achieved once the user obtains enough Blutz Waves from a moon or celestial body to transform into a Golden Great Ape and then maintains control of themselves upon becoming the Golden Great Ape, which automatically triggers the transformation into Super Saiyan 4. But after Pan helped Golden Great Ape Goku ascend to Super Saiyan 4 by reminding him about a time at the beach, Goku has been able to skip over having to become a Golden Great Ape entirely since then.
The same can’t be said of Vegeta. He needs to get zapped with Blutz Waves every time. Some fans assume that it’s because Vegeta doesn’t have a tail, but that argument doesn’t make sense given that he can already transform into a Golden Great Ape without one. All he needs are Blutz Waves. In episode 55 of Dragon Ball GT, Bulma theorizes that the only thing that was initially holding then-Baby Vegeta back from transforming into Super Saiyan 4 was that his body wasn’t strong enough to withstand the transformation, not because he didn’t have a tail initially. The tail only makes it easier to absorb Blutz Waves. The fact that Vegeta later becomes Super Saiyan 4 is proof this is true. So what a Saiyan truly needs are enough Blutz Waves and the ability to physically withstand the transformation. So the real question is how can Goku transform at all when there isn’t a celestial body that’s reflecting enough Blutz Waves?
Dragon Ball’s Super Water of the Gods Is Akin to Blutz Waves
The only answer that makes sense is that Goku drank the Super Water of the Gods in Dragon Ball. He already possesses the power of the Great Ape even without having to absorb any Blutz Waves. He just had to undergo the whole experience the first time when he became a Golden Great Ape, maintained control of his mind as a Golden Great Ape, and then transformed into a Super Saiyan 4. In other words, Super Saiyan 4 basically works for Goku as every other Super Saiyan transformation does for every other Saiyan. No other Saiyan needs to experience extreme rage and/or hatred to transform into a Super Saiyan every time. However, Vegeta doesn’t experience this with Super Saiyan 4, not because he needs a tail whose only purpose is to absorb Blutz Waves, but because he never drank the Super Water of the Gods. While Dragon Ball GT often gets flack for its changes to continuity, Super Saiyan 4 actually has its roots in classic Dragon Ball.
Dragon Ball is available in English on Viz.com.