Following is a Forward to the Future spacetime slip from http://paranormal.about.com/od/Doppelgangers/a/doppelgangers.htm.
In a case that suggests that doppelgangers might have something to do with time or dimensional shifts, Johann Wolfgang von Goethe, the 18th century German poet, confronted his doppelganger while riding on the road to Drusenheim. Riding toward him was his exact double, but wearing a gray suit trimmed in gold. Eight years later, von Goethe was again traveling on the same road, but in the opposite direction. He then realized he was wearing the very gray suit trimmed in gold that he had seen on his double eight years earlier! Had von Goethe seen his future self?