Are doppelgangers real?

If you've seen the Twilight Zone episode Mirror Image, you probably have asked yourself if there is another you out there. I did. I wondered if there was another me, just waiting to replace me. Unfortunately, I got my answer years later...

I lived in a small town and was a regular at the local gas station. I went in one morning to get a cup of coffee before work. The woman behind the counter smiled and asked if I'd forgotten anything. I laughed and asked how I could have when I hadn't been in there yet. She said I was just there a little while ago. I insisted it was my first trip that day. She was quiet for a moment, then said I have another me walking around. Another me that answered to my name and carried on a full conversation as me. This was very disturbing. I never saw the other me and she never went back to that gas station again, at least that's what I hope. I wonder if she's still out there?

Do you believe in doppelgangers? Have you seen your other you before?