I’ve got this doppelganger.  I’ve never come across him, but now and then someone stops me in the street and starts to talk as if they know me. I let them rattle on. It’s not worth explaining that they think I’m someone else.  One of my work colleagues has seen him, and for a moment she was almost taken in, only, when she looked closely she realized he was someone else. The resemblance is apparently uncanny.