I suppose philosophically “Who are you” is about what attributes, qualities, beliefs, memories and others things about you that are important to you personally, not to doctor or alien. Or, probably, in other words, which of this things makes you you.
I guess many people feel like they have some specific "consciousness" or "soul" which is not connected to any other particular attribute. So they can imagine themselves having other body, memories and beliefs while still being themselves, while other people consider some beliefs, memories, or even body as something critical for being themselves. (Or may be some people think that their "soul" have some qualities of Capricorn or anything other as variation.)
So I still wonder how any particular answer can be reasoned rationally, and also I'm not sure which practical implications it can have so I'm not sure if any clear explanation of question can be enough to make discussion really rational.
Really I can figure out some hypothetical situations, this question is related to. For example it can be important to make decision if capturing mental activity and copying it into computer system is acceptable way to become immortal, or any exact model of your brain activity will not be really you so it haven't much sense.
I also may notice that current materialistic model of universe can't make me sure even that today I am the same I that I was yesterday. So there is not much reason to claim that computer model of me is not me, just because i even can't claim that I'm me from previous day or even second or that group atoms which combine my body are any significant way different from any other atom group in universe. I only hope that it's all not much true cause current human's knowledge and intellectual power are probably just not yet enough to figure out all the true aspects of situation. But it still makes it's all more about religion and poetry rather than rationality.
How do you know that you do?