Several weeks ago, the new promotional anime, Dragon Ball Super Heroes, debuted in Japan. In the first episode, fans saw something they weren't sure they'd ever see again in anime form -- Super Saiyan 4 Goku. It's been nearly two decades since we last saw SS4 in anime action. During the interim, we've been treated to the form in other mediums -- namely, video games and manga -- but once the Dragon Ball GT anime concluded its run, it seemed we'd seen the last of it in anime form. All of that changed when the announcement came from Japan that they'd be creating an anime to promote their hugely popular arcade game, Dragon Ball Heroes. Now, fans have already seen the improbable return SS4, going toe-to-toe with Super Saiyan Blue Goku no less.

SS4's return to anime action is just the latest development in its recent resurgence in popularity. The form first debuted DBGT's episode, "Back in the Game". After DBGT finished up in November of 1997, SS4 was primarily kept alive in various DBZ video games. The game that did the most for SS4, Dragon Ball Heroes, arrived in Japan in 2010. The game explored an alternate Dragon Ball timeline, allowing it to bring in an assortment of new SS4 transformations, previously reserved for fan fiction. In 2012, a promotional manga for the game hit shelves, introducing SS4 in manga form for the first time. And now with SS4 having made its long-awaited anime return, it seems like the sky's the limit for the future of SS4. Here's everything you need to know about SS4 and its surprising revival.

15 SUPER SAIYAN-GREAT APE COMBO

Goku and friends found their first major enemy in DBGT in parasite known as Baby. Baby dispersed himself, allowing himself to possess most of Goku's allies. Ultimately, it was up to Goku to defeat Baby and his most powerful host, Vegeta, aka Baby Vegeta. Finding SS3 to be an insufficient means of defeating his newest enemy, Goku consulted with the Elder Kai and discovered a way to go beyond SS3.

The process involved first transforming into a Great Ape -- a Saiyan form last seen at the beginning of Dragon Ball Z. From there, Goku reverted back into an adult form as an SS4, his body now encapsulating the power of a Great Ape and Super Saiyan.

14 SUPER SAIYAN X 10

It goes without saying that SS4 is more powerful than preceding Super Saiyan forms -- but just how powerful? While in SS3, Goku could hardly damage Baby at all. Fast-forward to Goku achieving SS4, and the tables had completely turned; now it was Goku toying with Baby, the latter practically incapable of landing a punch.

A more exact description of SS4 was given in Dragon Ball Z: Scouter Battle Taikan Kamehameha -- a Japanese DBZ video game. In the game, SS4 is said to be ten times as powerful as the original Super Saiyan form. This lines up with the title of one of SS4 Goku's signature techniques, the 10X Kamehameha.

13 ALWAYS TAKES ADULT FORM

Dragonball GT kicked off with Goku's lifetime nemesis Pilaf using the Black Star Dragon Balls to turn Goku into a kid. Goku's sudden de-aging set off his journey to recollect the Dragon Balls, so they he could return to adult form. However, it turns out that Goku didn't have to wait for his magical wish to grow up again.

Upon achieving the Super Saiyan 4 transformation, Goku automatically grew into an adult. Unlike Super Saiyan 3, which he easily achieved as a kid, Super Saiyan 4 was apparently off limit to kids. Super Saiyan 4's unexpected condition was reinforced by the fact that Goku returned to being a kid every time he depowered from the form.

12 CAN'T BE ATTAINED AT WILL

It takes a lot for a Saiyan to reach any new level of power. Goku and his fellow Saiyans have to train arduously for years to achieve new forms, and even when they have the potential, they have to power up at length in order to manifest the new form. It's even more difficult to attain SS4.

A Saiyan must transform into a Golden Great Ape and then gain conscious control over the beast to be able to access SS4. But even after one has reached the form before, the form cannot be accessed will. In most cases, a Saiyan must be subjected to Blutz waves in order to tap into the power.

11 VEGETA CHEATED

Fans of everything Dragon Ball will know that Vegeta's defining character trait is his pride. The prince of all Saiyans repeatedly refers back to his royal heritage and boasts about his incredible power throughout DBZ. Unfortunately, to the dismay of many fans, Vegeta wasn't featured as heavily in DBGT.

Towards the series' end though, he nabbed the spotlight by transforming into SS4 -- albeit through uncharacteristic means. Putting his pride aside, Vegeta resorts to using a machine created by Bulma in order for him to attain SS4. The turn of events stunned long-time fans as it seemed that Vegeta used the Dragonball equivalent of performance-enhancing substances.

10 DESIGNED BY KASTUYOSHI NAKATSURU

One of the most famed character designers of the Dragon Ball franchise, aside from series creator Akira Toriyama, is Katsuyoshi Nakatsuru. Toriyama has praised Nakatsuru's impeccable ability to mimic the series creator's art style, exclaiming that sometimes he can't tell if he or Nakatsuru was behind a certain design. Nakatsuru, who worked alongside a team of character designers from DBZ Cell arc, onward, received sole character design duties for DBGT.

While working on DBGT, he'd create his one of his most recognizable designs, SS4, perhaps only rivaled by his design of Goku's father, Bardock. Fans may also recognize his work on the cover art of Dragon Ball Z: Budokai series of video games.

9 CLOTHES MAGICALLY CHANGE

In addition to becoming an adult when entering into SS4, Goku's clothes also magically change. Specifically, after transitioning into giant ape form, his clothes understandably disappear. When Goku transitions from giant ape to SS4, his pants reappear and once returned to base form, his top magically returns as well.

No explanation is given for this. The inexplicable altering of clothes must be assumed to be some strange side-effect of SS4, which has already shown itself to be vastly different from preceding Super Saiyan forms. The magical change of clothes remains consistent with other SS4 users, notably Gohan's SS4 transformation in Dragon Ball Heroes and Vegeta's transformation in DBGT.

8 INCONSISTENT AURAS

Super Saiyan 4's aura seems to be constantly changing, mainly due to who's taken the form and the medium through which the characters are shown. When Goku first attained SS4, the aura was similar to the yellow aura of the original Super Saiyan form -- the electricity characteristic of SS2 and SS3 was gone.

The aura held consistent when Vegeta reached SS4 later in the series. However, the video games displayed the aura differently. In the Xenoverse and Budokai series, SS4 users emanated a red aura, shooting off sparks of electricity. Gogeta also displays electricity within his aura when he appears in SS4 during the concluding arc of DBGT.

7 SS3 REQUIRES MORE ENERGY TO MAINTAIN

Despite being vastly more powerful than SS3, SS4 requires less energy to maintain. Whereas SS3 takes an extraordinary amount of ki to maintain, resulting in a serious toll on its user, SS4 doesn't require as much ki due to its special condition. This explains why Goku is shown in SS4 for long periods of time during the series as opposed to the brief spurts with which SS3 was seen before.

Naturally, after SS4 was introduced, SS3 became irrelevant (Vegeta even opted to skip SS3 altogether). Although SS4 has its own hassles to contend with, SS4, when achieved, takes the cake over SS3 on every level.

6 REDUCED FUSION DURATION

Gogeta, who'd only previously been seen in Dragon Ball Z: Fusion Reborn, made his unexpected return to the mythos in DBGT's "Super Saiyan 4 Fusion", in SS4 no less. Goku and Vegeta, still having trouble defeating Omega Shenron, employed the Fusion Dance technique. Gogeta was thus reborn, now in SS4, sporting red hair and covered in brown fur.

Too powerful for his own good, SS4 Gogeta toyed with the now pitiful-seeming Omega Shenron, thinking that they had plenty of time before the fusion wore off. However, the fusion lasted merely ten minutes to the astonishment of its participants. Turns out, the incredible power of SS4 Gogeta came with a reduced fusion period.

5 SS4 PROTOTYPE APPEARED IN DBZ

Vigilant fans have discovered a brief scene from DBZ that foreshadowed the awakening of SS4. The scene is from Goku's first transformation into SS3, during the Buu Arc. Right before Goku achieves his new state, a vision runs through his mind.

He sees himself evolving from a Great Ape to an ape-Saiyan hybrid to his normal adult form and then back to a baby. The ape-Saiyan hybrid appears to be an SS4 prototype. Fans also wonder if it was mere coincidence that the form followed a Great Ape. Did the crew behind DBGT find inspiration in this fleeting moment from DBZ?

4 LIST OF SS4 USERS IS GROWING

After DBGT concluded in 1997, fans weren't sure if they'd ever see another Super Saiyan 4. Save for some movies and video games here and there, the Dragon Ball series seemed to be winding down. Without a new anime or manga, new merchandise could only be expected to gradually die off. However, all of that changed during the 2010s.

Japan's massively popular arcade game, Dragon Ball Heroes gave fans everything they ever dreamed of, including new SS4 transformations. The game (and eventual promotional anime) explored an alternative Dragon Ball universe -- fans were treated to an SS4 Broly and SS4 Gohan, and the list keeps on growing.

3 MADE MANGA DEBUT 15 YEARS LATER

One more peculiar thing about SS4, which set it apart from the preceding Super Saiyan forms, was that it originated in the anime. Unlike Dragon Ball and Dragon Ball Z, DBGT was exclusively an anime -- it was neither based on a manga nor received any manga adaptation.

For that reason, it didn't look like SS4 would ever be introduced in manga form. Then in 2012, a manga spun off from the Dragon Ball Heroes game hit shelves. Entitled Dragon Ball Heroes: Victory Mission, the manga saw SS4 on the page for the first time. The issue sees Goku transform into SS4 to help in a battle against Super Baby Vegeta.

2 RETURN TO ANIME

After Dragon Ball GT began in 2015, it became increasingly clear that creator Akira Toriyama was disregarding DBGT altogether. With Super Saiyan God and its many variations taking over the Dragon Ball anime, it looked as if SS4 would be relegated to video game the only status.

That all changed with the Dragon Ball Heroes promotional anime. The anime, aimed at directing more fans to the video game, saw the return of SS4 Goku in its first episode. If that weren't enough, SS4 Goku went toe-to-toe with Super Saiyan Blue Goku, providing fans with the fight previously reserved for fan fiction.

1 ISN'T TORIYAMA CANON

The question of whether or not DBGT is canon has been long-standing controversy among Dragon Ball fans. However, the accumulating evidence from recent years of new Dragon Ball material indicates that the series doesn't take place in the main continuity which DB, DBZ, and DBS take place.

The primary reason for this is that the creator of the aforementioned Dragon Ball series, Akira Toriyama, had little to do with DBGT. Plus, the latest series, DBS, would have to take place between DBZ and DBGT, and it seems that too much has transpired during DBS for it to mesh with DBGT.