There is evidence to suggest that Ditto is a failed clone of Mew. Both Pokemon are genderless, weigh the same, their base stats are exactly the same in every respect, they share almost identical colors, and they're the only two Pokemon who learn Transform naturally.

Ditto can also be found commonly in the same cave as Mewtwo, as well as the mansion on Cinnabar Island, where experiments on Mew were said to take place.
Contributed by DidYouKnowGaming