Alright, we all know the glitch Pokemon. Decamark, Missingno, Bad Egg, DPBox, 3TrainerPoke, 'M, .4, Q, A, etc. etc. etc. But there's one question about them that has never been answered:
How would they fit into the Pokemon world?
I have made an entire fanfiction answering that question. I'm not going to be posting it, but here's the general idea:
So, we know that Arceus was made from an egg amongst endless chaos, right? And we also know that Arceus created Dialga, Palkia, Giratina, Azelf, Mesprit, Uxie, and Mew.
However, if you woke up, and had the power to create anything, you would make mistakes before you got it right, am I correct? Well, that's what the glitches are. They were Arceus's first attempts at making Pokemon. However, he failed miserably, and thus made the monstrosities that we know as the glitches.
Arceus saw the glitches as dangerous due to their hatred of him, mainly because they were his "failures". So, Arceus banished them to a corner of the universe, one nearly unreachable, and one they would eventually corrupt. Arceus banished the glitches to what would become Glitch City.
The glitches wanted to extend their power, and more importantly, get rid of Arceus. So, once they reached the Pokemon world, being extremely powerful creatures, (if you could call them that) their very presence causes a fair amount of "glitches" to crop up in the world.
Comments, suggestions, questions?