I am a figment of my own imagination.
I am also a figment of your imagination, since we have never met.
Schafter lists seven "sins of memory"; transience, absentmindedness, blocking, misattribution, suggestibility, bias (rewrite previous experiences in light of what we now believe) and persistence. Misattribution - incorrectly assigning a memory to a wrong source, mistaking fantasy for reality, is far more common than we like to admit.