An episode of the legendary
television series The Prisoner. In it, our
protagonist Number 6 is 'replaced' by a
body double, and is given
brainwashing to make him believe that he is the duplicate of himself in order to confuse him and make him confess
why he resigned. The phrase is also the
password used in this episode to allow the speaker past the security robot known in the series as
Rover.
One of my favorites of the 17 installments of one of the best shows ever made. There is an episode of Star Trek: TNG entitled The Schizoid Man which, I believe, is done in homage to this series.