Just a little theory, dealing with Mew and Ditto.
As you know, Mew is the ancestor to all Pokémon upon the Pokémon World, barring the Sinnoh lot. Now, Mew could learn any move, but are commonly depicted able to use Transform. I don't know about you lot, but I figure if Mew were the ancestor to all Pokémon, thereby being the only existing Pokémon at one point, you'd expect them to be a bit more common, yet they aren't...while Ditto are. Ditto share Mew's colour scheme, as well as their ability to (albeit temporarily) learn any move in the Pokémon World. One can also argue Ditto have the DNA of all Pokémon, since they would need it to know what goes where, like a reference sheet, inanimate objects not counting, as they aren't exactly complex when compared to living creatures.
However, there are a couple of arguments against this theory, such as "If this is the case, why don't Ditto remain in the form of Mew when they Transform, thereby regaining their form". Well, one could argue that whatever reason that caused them to loose their form may prevent them from keeping a solid form, which also serves as to why Ditto don't remain a Pokémon they've copied after battle, for the trainer's convinience.
And for a bit of botched game programming being used in the argument, if you catch a Mew that's used Transform in Gen 1 and 2, then you'll end up with a Ditto instead.
Discuss, or trash if this is "that topic again..."
Edit: Ok, so people who've just read the topic can see the newer facts without having to go through all the pages, I'll list them here:
Also, the information partaking to the Generation 1 and 2 Transformation Glitch was a joke on my part. I'm pretty sure that if a Smeargle copies Transform and uses it, it will also become a Ditto. I state this because some people don't apparently view it as a joke, but rather a legit argument. If I had intended for that, I would have made it more prominant.Originally Posted by Reasoning for the theory