Paper Mario: The Origami King is a good time, as you'll know from our review. However, there are fans of the series who aren't pleased by the fact that it lacks any kind of experience or levelling system – especially as it's pitched as a proper RPG experience, as several other entries in the franchise have been.
However, it would seem that EXP was considered for the game at one point. A variable called "battle_win_exP’" is actually mentioned in the save file data, which you can open using a text program on your computer – it's not even hidden or concealed.
Of course, having that value in the save data doesn't mean Paper Mario: The Origami King was necessarily going to have a traditional EXP system – it could have been handled in a wide range of ways. However, the existence of the variable does at least hint that the game underwent some gameplay changes close to release.
Would you have liked to have seen a more old-school EXP system in the game? Tell us with a comment.