Who or What are the doppelgangers?

[Wallfire]

Back in the late 80s wile I was working for a week in another city I seen a woman whos brother I knew. I was a bit surprised to see she was pregnant but not something that meant a lot to me so I just did not even think about it. By chance we met again at a cafe, she did not look pregnant so I stuptly asked her if she was. She answered  that she was NOT and why did people keep asking her this. So I went to my table and though no more about it.
Only now when I read this tread did  think she might of had a doppelganger