Memento: The Manufactured Quest
Memento employs two alternating timelines: a forward-moving black-and-white sequence and a reverse-moving color sequence. They converge in the derelict building where Leonard Shelby shoots Teddy (Joe Pantoliano).
The profound twist of Memento is not that Leonard suffers from anterograde amnesia, but that Leonard is his own antagonist. In the chronological turning point (the final color sequence on screen), Teddy reveals that Leonard already tracked down and killed the authentic attacker a year earlier.
Leonard cannot survive without a purpose; peace offers only empty grief. To keep his life animated by righteous vengeance, Leonard consciously notes Teddy’s license plate on a scrap of paper, labels Teddy a liar, and writes the instruction that will inevitably cause him to execute Teddy twenty minutes later in film-time.
The Sammy Jankis Insane Asylum Flash
At timestamp 01:29:40, as Leonard sits in the mental institution narrating Sammy Jankis’ deterioration, someone walks across the foreground. For exactly four frames (one-sixth of a second), Sammy's face is replaced by Leonard Shelby sitting in the patient chair. Leonard did not witness Sammy administer fatal insulin doses to his wife—Leonard administered them to his own wife.