Ferdinand Waldo Demara Jr. lived for 60 years, and spent most of them pretending to be someone else. Or someones else, really; the man who came to be known as “the Great Imposter” adopted at least 10 identities, including a year-long stint as a (self-taught!) trauma surgeon during the Korean War.
You're looking at a woman who resembles your mother. She moves and talks like your mother, and she's even dressed the same as your mother. In fact, she is your mother. But you're absolutely certain that she's an imposter.