Thought I'd give this a go. I a Gen-Onner I fully utilized the MissingNo Glitch when I played Pokemon Red and Blue to get myself unlimited MasterBalls and Rare Candies. I never realized how popular a 'Semi-Fakemon' It had become until I decided to Google it. I thought I'd give it my own form and Dex entry.

Being found along Cinnabar Island I thought it could quite easily slot into the Mewtwo Lore as a Legendary in it's own right and turns out I'm not alone in that, as many people seem to have used that arch to give it a story of it's own. I think it would be so cool to actually have MissingNo turned into an actual Mon since it's such an iconic thing in the early Pokemon Games. It could have a Legendary Movie to I think.