An event which seems unbelievably contrived - so much so that when it happens to you, you begin to suspect that you are not a real person, but a character in a celestial sitcom.
(from a Lucy-Desi Comedy Hour episode, ca. 1956) You are in Las Vegas and you and the Mertzes want to go on a uranium hunting expedition in the desert, and children are not allowed. You then discover that a couple you know from New York is staying in the same hotel with their child. Little Ricky then goes to Hoover Dam with the other couple and their child, freeing you to hunt for uranium. The "Truman Show moment" occurs when you discover that the other couple is at your hotel.