Katy Perry -- I Have A Twin! And I Like It

Katy Perry doesn't need a mirror any more ... because she just found her long lost twin.

Okay, so they're not identical, but pretty DAMN close ... outside the world premiere of "Katy Perry: The Prismatic World Tour" in L.A. Thursday night, Katy did a double ... nay ... triple take as one familiar looking fan stepped up for a selfie and threw everyone for a loop.

Same eyes ... check ... same eyebrows ... check ... Kitty Purry outfit ... check.

Hey, if her doppelganger can strut and lip sync, the real Katy could take a break from the road every now and then.

Meow-be? Meow-be not.