This takes us to the “Z” portion of the story, which naturally brings up the whole reasoning behind the name “Dragon Ball Z” to begin with. In his joint interview with veteran animator Katsuyoshi Nakatsuru in the anime guide Son Goku Densetsu, Toriyama explained that he personally felt the name of the series was just fine the way it was, but the anime staff wanted something new for this new section of the story, and so “Dragon Ball Z” was born. As Toriyama explains, “Z is the last letter in the alphabet, right? So, at the time I already really wanted to end the series, and so I made the title ‘Z’ to say ‘Hey, this is the end!'”
It would seem that with all this talk about the series only continuing on for “just a little bit more”, and the “Z” in the anime title being a signal that this was the end, it would be reasonable to speculate that at the time Toriyama expected the Saiyan story arc to be the last one. This is not a theory tossed out often, because the Saiyan story arc ultimately ended up leading directly into the Freeza arc. It is not necessarily true that this was the plan from the beginning, and certainly there are plenty of signs in the Saiyan arc that Toriyama had not thought of Freeza yet. Planet Vegeta’s destruction is initially said to have been caused by simply a meteor collision (even ignoring contradictions exclusive to the TV adaptation of the series), while later on Freeza is said to have been the true cause. Vegeta and Nappa change their plans and head to Earth as if they were their own bosses; in the Freeza arc this action is said to have been in defiance of Freeza’s orders, something not even hinted at in the original scene. Also, Vegeta originally proposes that he and Nappa wish for immortality so that they can enjoy battle for all eternity, while in the Freeza arc Vegeta’s motive for obtaining immortality is changed to being so that he can defeat Freeza. In the Saiyan arc, the Saiyans are said to be the strongest race of warriors in the universe, and Vegeta personally claims to be the strongest in the universe while fighting Goku, while in the Freeza arc we are introduced to many members of alien races who are stronger than the Saiyans, and Freeza is now said to be the strongest in the universe.
None of these things are necessarily plot holes from an “in-universe” perspective (the story of Planet Vegeta being destroyed by a meteorite is said to be just Freeza’s cover story, claims of the Saiyans being strongest would just be signs of Raditz and Vegeta’s arrogance, etc), but from a real world perspective they all point to Toriyama having not originally planned on Freeza or his organization appearing while he was first writing the Saiyan arc. It is not until the tail end of the Saiyan arc that we first start having hints of Freeza, with Kaiō vaguely noting that killing Vegeta will not destroy “the roots of evil”. There is however a bit of an obstacle in thinking that Toriyama did not already have some inkling of the Freeza storyline in mind when writing the Saiyan arc. In his Daizenshuu 4 interview, when asked whether he intended from the very beginning that Piccolo would be an alien, he answered:
Of course, I didn’t think that at all (laughs). The Saiyans were like that as well. When I thought up Goku’s tail and the Ōzaru, I didn’t think Goku was an alien or anything. Piccolo either. Because I thought that up when God came out.
Even though he had not planned on Piccolo being an alien from the beginning, he still had already come up with the idea before the 23rd Tenka’ichi Budōkai even began, long before the fact was finally revealed in the series (it would also therefore seem then that Piccolo and God’s conversation at the tournament was from the beginning intended to be Namekian and not simply some strange, random language).
If Toriyama had Piccolo’s alien origin planned out ahead of time, would that not also mean he had the Freeza arc planned out too? Not necessarily. For one thing, it is possible that Toriyama did not originally intend for the cast to travel to Piccolo’s home planet and have adventures there. After all, it is not as if the revelation of Goku’s alien heritage led to a trip to his home planet. For an outside perspective, take the Tenchi Muyo! series: throughout the numerous Tenchi OVA, TV series, manga, and movies with their various different continuities, the planet Jurai is almost always home to many of the main characters, yet story arcs that involve the cast actually journeying to Jurai are fairly scarce. It is also quite possible that Toriyama did come up with a storyline set on Namek early on, but only thought up Freeza later. We have seen above how there are signs that Toriyama might not have had Freeza in mind when he first began the Saiyan arc, while we also know for a fact that he came up with the idea of Piccolo being a Namekian long before the Saiyan arc even began. Perhaps the trip to Namek was originally just going to be a short second half to the Saiyan arc, with Vegeta still being the main villain? Or even just a brief epilogue to the series without any real conflict, like the 28th Tenka’ichi Budōkai at the end of the Majin Boo arc?
It seems hard to reconcile the massively long Namek/Freeza arc which we know today with Toriyama’s stated desire that the series only continue for “just a little bit” past the 23rd Tenka’ichi Budōkai. As it turned out, the Saiyan and Freeza arcs ran from 04 October 1988 with the release of chapter 195 in Weekly Shōnen Jump, all the way up to 11 June 1991, with the release of chapter 328 — that makes 32 months, over two-and-a-half years. Meanwhile, the run of the series from the beginning up the end of the 23rd Tenka’ichi Budōkai was 46 months, from 20 November 1984 to 27 September 1988 — if you had been drawing a series for close to four years, drawing it for nearly another three years would not really constitute continuing “for just a little bit”. It is probably safe to say that the Freeza arc as it stands is not really what Toriyama originally had in mind. It is anybody’s guess though as to whether that is because he was not planning on having it at all, or originally envisioned a far shorter and therefore drastically different version of it.
What caused him to continue it on so long? Popularity is again the most obvious candidate. As Toriyama said back in Tankōbon Vol. 7, because of “all the support I’m getting, it seems that I can’t end [Dragon Ball]”. The series was already very popular by the time the Saiyan arc began, and it only took off even more afterwards. It is not for nothing that the “Z” portion of the series gets all the attention it does overseas, and even in Japan these days with Dragon Ball Kai and all the video games. In Shenlong Times #1, Toriyama’s later editor Fuyuto Takeda noted that his predecessor Yū Kondō “became the editor right around the time the Saiyan arc began. At that time, Dragon Ball was explosively popular”, and in Shenlong Times #2 Takeda notes that Kondō came on “when [Toriyama-]sensei began to try and make Dragon Ball more popular through its storyline, and it certainly bore fruit”. The standard story told via Internet rumors is that Dragon Ball‘s popularity forced Toriyama to continue past the Freeza arc, and as we will see in its simplest form this rumor is not really false, but it is far from the whole truth. In reality, it was Dragon Ball‘s massive popularity that forced Toriyama to even draw the Freeza arc to begin with!