Hear me out: a "Wild West" ditto, which looks like a regular ditto but with a moustache and cowboy hat, and when it transforms it looks just like the target pokemon, except with a moustache and a cowboy hat added on.
Unfortunately I have no artistic talent so cannot provide sketches at this moment, but I intend to start a gofundme to commission the concept art sooner or later.
That's a funny little concept. Not smth that would ever be cannon but funny regardless. Might not work on every pokemon tho.