The much loved feature of having your favorite Pokémon follow you in the overworld was probably planned to be included in Sun and Moon according to recent findings.
The feature, inspired by Yellow and then debuted in Platinum/Diamond/Pearl with the Pokémon Amity Square, was then featured in full in Pokemon Heartgold and Soulsilver. Now, for good reason, fans won't let Gamefreak forget it exists and push for it in every game.
Well, it looks like it was supposed to be in SuMo.