Seriously. I think there might be a possibility that he is cannon. Lets add what we know about MissingNO to this.1. Appears in some from, in every Pokémon game, except Diamond-Black - While it's not always the same form, there's still the possibility of encountering a glitched battle, either with an empty slot in the game (RSE-FR) or something else (RBY-GSC) And in Y, he makes an appearance in his best known form in Lumiose.2. He is based off your character name. - There is a reason that particular MissingNO was attracted to you. There are many MissingNO out there, but the one who is attracted to you, is that way because of one simple reason. (I'll get to that later)3. His type can vary - I'll explain this in a bit too.Now, lets add this to player theory1. MissingNO is what happens when Pokémon are left inside their respective balls for too long. The data becomes corrupt, and everything changes. Pokéballs change physical forms to data, so it is simple to explain how this would happen. Why were they left in there for so long? Either the Trainer has died, lost his Pokéball, or just forgot him.MissingNO would be attracted to certain players who share the name with their previous Trainer. As a gift for seeing you once more, he grants you many items (in your 6th slot) While catching him could change some things, he feels at home again.MissingNO, like normal Pokémon, eventually die. Since MissingNO is corrupted, they fade away into nothing, unless they are caught. If caught, they can stay a little while longer, because they're happy again. Some can even be restored to an extent through evolution.The MissingNO in Y is simply a Cameo, probably for Fan Service. However, the fact that Game Freak has not yet let him go gives the feeling that they have something in store for us in the future.
Seriously. I think there might be a possibility that he is cannon. Lets add what we know about MissingNO to this.1. Appears in some from, in every Pokémon game, except Diamond-Black - While it's not always the same form, there's still the possibility of encountering a glitched battle, either with an empty slot in the game (RSE-FR) or something else (RBY-GSC) And in Y, he makes an appearance in his best known form in Lumiose.2. He is based off your character name. - There is a reason that particular MissingNO was attracted to you. There are many MissingNO out there, but the one who is attracted to you, is that way because of one simple reason. (I'll get to that later)3. His type can vary - I'll explain this in a bit too.Now, lets add this to player theory1. MissingNO is what happens when Pokémon are left inside their respective balls for too long. The data becomes corrupt, and everything changes. Pokéballs change physical forms to data, so it is simple to explain how this would happen. Why were they left in there for so long? Either the Trainer has died, lost his Pokéball, or just forgot him.MissingNO would be attracted to certain players who share the name with their previous Trainer. As a gift for seeing you once more, he grants you many items (in your 6th slot) While catching him could change some things, he feels at home again.MissingNO, like normal Pokémon, eventually die. Since MissingNO is corrupted, they fade away into nothing, unless they are caught. If caught, they can stay a little while longer, because they're happy again. Some can even be restored to an extent through evolution.The MissingNO in Y is simply a Cameo, probably for Fan Service. However, the fact that Game Freak has not yet let him go gives the feeling that they have something in store for us in the future.