1- Vivi being a Princess.
2- Shanks appearing in Marineford War.
3- Portgas D. Ace being Gol D. Roger’s son.
4- Rob Lucci being villain.
5- Doflamingo and Corazon having blood relationship.
6- Shichibukai appearing in the manga. One Piece was originally supposed to be a story to fight Yonko, not Shichibukai.
7- Supernovas still surviving in New World. Oda thought about half of them would have dropped out already.
8- Trafalgar D. Water Law being an important character. Oda thought Eustass Kid would become an important character, though.