The original sketches for Dragon Ball's Super Saiyan 3 inspired the design of Dragon Ball GT's Super Saiyan 4. Akira's Toriyama raw sketches for Goku's Super Saiyan 3 form, published in Dragon Ball 30th Anniversary Super History Book, show that the original design for that iconic form included a feature that would later define Goku's equally iconic, and controversial, transformation in Dragon Ball GT.
In the entire history of the Dragon Ball franchise, the two most debated transformations used by its characters must be Super Saiyan 3 and 4. Super Saiyan 3 made its debut in the final part of Dragon Ball Z, the Majin Buu saga. It immediately stood out due to its unique design, which noticeably changes the features of whoever is using it, but it also failed to impress due to the inherent limitations of this form. In fact, Super Saiyan 3 never managed to win a fight, a terrible record for what's supposed to be the strongest Saiyan form in the original series. Super Saiyan 4 changes the aspect of the user even more, sporting the tail and fur of the Saiyans' Great Ape form. However, because it was only used in Dragon Ball GT and in the video games-derived media, the canonicity of this transformation is still debated today by fans.
Only the most knowledgeable Dragon Ball fans know that Super Saiyan 3 and Super Saiyan 4 actually share a big connection. The Dragon Ball 30th Anniversary Super History Book is a special volume that commemorates the glorious history of the franchise. It contains information, interviews with Akira Toriyama, and even a collection of preparatory sketches that the mangaka realized during the original serialization of the manga. One of these sketches shows Toriyama's original design for Goku's Super Saiyan 3 form. It looks almost identical to what later appeared in the manga, with one big difference: Goku has grown back his tail in this form, just like he does in Super Saiyan 4.
Super Saiyan 3 And Super Saiyan 4 Have Many Common Features
The original sketch for Super Saiyan 3 did not meet the approval of Toriyama's editor at the time, who suggested removing the tail. A few years later, Dragon Ball GT's character designer, Katsuyoshi Nakatsuru, was inspired by that design to create Super Saiyan 4. The similarities between the two forms, however, do not stop at the tail. Both Super Saiyan 3 and 4 make the user's hair grow noticeably. Facial features also change (more noticeably in Super Saiyan 3) and in both forms Goku takes a more serious and menacing look. In Super Saiyan 3, however, eyebrows disappear, a feature that was not picked up by Super Saiyan 4 but actually came back years later in Dragon Ball Super as a noticeable trait of Vegeta's Ultra Ego form.
While Dragon Ball GT has been declared canon by both Toriyama and Shueisha, it seems unlikely that Super Saiyan 4 will make its debut in Dragon Ball Super. The new series is moving away from Super Saiyan transformations to focus on the more effective God Ki forms, such as Ultra Instinct and Ultra Ego. However, it is still very interesting to learn that the famously ineffective Super Saiyan 3 has inspired another much-debated Dragon Ball transformation, Super Saiyan 4.