It's you!
Well, it looks like you... but... you're you, aren't you?
Duplica is a Ditto, but not just any Ditto, through some weird quirk of her (despite being technically genderless, she identifies as female) genes, or perhaps due to incredible talent, Duplica is able to perfectly replicate pretty much anyone that she sees, right down to their voice, though it doesn't give her some kind of psychic sense, so while she can attempt to mimic a person's mannerisms, it's pretty much all up to her acting ability, and due to the fact that she's pretty quirky, she has difficulty maintaining such a facade for very long.
Duplica's body allows her to take certain liberties as well, and while it's easiest to look identical to someone, she's entirely capable of making certain enhancements, whether it's bigger breasts, smaller waist, rounder ass, or a little extra equipment between the legs (either or both genders), she can alter herself however she might desire, within certain limits that even she isn't even really aware of.
It should also be noted that while Duplica is perfectly fertile and able to reproduce with pretty much any living being, she isn't terribly fond of the reputation of her kind, and has therefore chosen to abstain from sex until she finds "the one," whoever or whenever that might be...
For those of you interested in Pokemon stats:
Level: 100
Nature: Quirky
Ability: Imposter
Held Item: Quick Powder
Moves: Transform (duh)
Also, she's another of the Silhouette_Alts