Eiichiro Oda, the author of One Piece, is known to plan his story quite meticulously. He is especially known among both anime and manga fans as an author who likes to plant his seeds early and then elaborate on them at a later point in the story. Oda is also exceptionally good at foreshadowing. While all these qualities are incredible, a writer doesn't always need to plan things in advance to be great.
In fact, there are several incredible moments in One Piece that have only been possible due to Oda making very late changes to his initial plans. Some of them have redefined One Piece and made it as great as it is today and without these decisions, perhaps the story would have been very different.
8 The 11 Supernova
One of the major decisions that Oda took at the very end was related to the 11 Supernovas. Oda introduced them to the fans in the Sabaody Archipelago arc. However, initially, there were no plans of introducing these characters.
Oda's editor mentioned to him that he felt the arc was not interesting enough and then, in a few hours, Oda came up with the designs for the 11 Supernovas and their complex abilities. Had he not done that, One Piece would have been very different today, given how important a role the members of the 11 Supernovas have played in the New World.
7 Vivi As The Princess Of Arabasta
Vivi is a beloved character among the fans and she was central to the story in the Arabasta Saga. It is surprising to know that Oda originally did not intend for Vivi to be a Princess at all. His plans for the character were entirely different and it goes without saying that her role would not have an as pronounced either.
Had Vivi not been linked to arabasta, she would certainly not have been an important part of the story. Thankfully, Oda decided otherwise and made her A Princess, which eventually gave fans so many brilliant moments across the Arabasta Saga, and now draws connections even to Imu.
6 Lucci As A Villain
There are many decisions that Oda has taken based on his gut feeling and making Lucci a villain is certainly one of them. In the Water Seven Saga, Oda had already decided that Franky would end up joining the crew, however, he did not decide on who was supposed to be the bad guy.
It was after introducing Lucci that he decided that he would make the guy with the pigeon a villain just because he felt like it. Consequently, fans received one of the very best villains in the entire series and this character remains iconic to this day.
5 The Appearance Of The Shichibukai
The Shichibukai were originally not planned to appear in One Piece at all. In fact, Oda wanted the story to be focused on the fight against the Four Emperors. It is unknown where exactly Oda decided to come up with the Shichibukai, however, it has to be early in the story as they were introduced during the Baratie arc. The Shichibukai has changed the course that the story of One Piece has taken forever.
These characters are incredibly important to the overarching plot of the story and fans are glad that Oda decided to include them.
4 Shanks In Marineford
One of the most hyped moments in the Marineford war is the appearance of Red-Haired Shanks towards the end. Shanks ended up stopping the war and this iconic moment has been etched into the hearts of the fans forever.
Originally, however, Oda did not want to include Shanks in Marineford War at all. It is unknown at what point Oda decided to include him, however, when the arc began, he certainly did not have any such plans for this character.
3 Doflamingo And Corazon Having A Blood Relationship
One Piece's Dressrosa arc focused heavily on the characters of Doflamingo and Corazon. The former was the main antagonist of the arc and had his entire life revealed to the fans through flashbacks. Doflamingo's flashback, coupled with that of Law, is very intriguing and possibly one of the best parts of the arc.
It is surprising to know that Oda did not initially intend for Doflamingo to be Corazon's blood brother. While Corazon was certainly going to be involved in the arc, he would not have been a blood relative to Doflamingo. Taking away that blood relationship would have changed fans' perception of these two characters.
2 Law's Importance
Trafalgar Law is a very important character in One Piece and he is actually one of the most popular ones among the fans. This is due to his popularity skyrocketing after the timeskip, where he sailed with the Straw Hat Pirates and had his entire story revealed to the fans.
The truth is, Oda never intended for Law to be this popular. Initially, Oda didn't have any grand plans for him at all. He wanted Kid to be popular, however, Law being as popular as he is today and receiving so much focus has actually surprised him just as much.
1 Ace Being Roger's Son
Quite possibly the biggest last-minute storytelling change that Oda has made in his story is to make Ace Roger's biological son. When the Marineford arc was being worked upon, Oda didn't know that he'd make Ace Roger's son.
At this point, Ace and Luffy were actually blood brothers. However, Oda asked his editor how he would feel if Ace was revealed to be Roger's son. The reaction he got from the editor pleased him and he decided to go ahead with it. This decision changed the course of the story forever.