Disclaimer: I do not own Pokemon.
By Silver Sailor Ganymede
It had no fixed shape or form; it was the only way it had managed to survive, through imitation, through illusion. What powers did the Ditto have in its natural form? It was nothing other than a genetically unstable blob in reality, but it could become anything it wanted if it tried. That was why some trainers used them so proudly, because the Ditto could become anything if it was told to do so: but perhaps it was more to do with the fact that those trainers were truly as unstable was the Ditto themselves.
Those that kept Ditto were quite possibley the greatest dreamers of them all; they wanted to be like the Ditto, to be able to become anything other than what they themselves already were. What a gift it would be to be able to become anything and everything you wanted, yet what a curse it would be to have no identity: of course few people would ever take that curse into consideration.
The curse was what made the Ditto so succesful, but in the end it was nothing more than an illusion.