Throughout history, meeting a doppelganger could only mean bad luck and was considered as an evil omen by many folklore tales. A doppelganger was seen as a malevolent twin or even a paranormal entity. The science behind these twin strangers is also quite grim as heautoscopy or hallucinations of seeing your own body in the distance might be signs of schizophrenia and epilepsy, which explains why it was seen as a harbinger of bad luck in the olden days. Thankfully, today we use the term doppelganger in a more general and neutral way to describe a person who looks or acts the same way as we do.
Bored Panda collected a list of people who experienced this bizarre lookalike phenomenon, and it looks like there's genuinely a glitch in the Matrix. Just think about it. You inherit the looks of your ancestors, and someone happens to look exactly like you and you happen to meet him accidentally. What are the odds? And though it is a quite an eerie experience, the chance for a fun picture is just too good.