[He blinks, hardly having noticed, and takes a step back. Okay... the fact that this pony isn't actively needling him at the moment is pretty good evidence that she can't just be Rainbow with hair dye. Mane dye? Whatever.]

Yeah, I'm fine. [He rubs his neck uncertainly. There isn't really any way of finding out short of asking, is there?] Hey, I know this is a weird question, but, uh - you got any relatives around here? 'Cause I know someone who looks a lot like you.

[It's not the only possibility he can think of, but the idea of multiple parallel worlds filled with physics-defying ponies gives him the overwhelming urge to... well, he doesn't know, break furniture or something.]