An event or series of events where you get feeling that people are watching you or even trying to alter your thoughts or actions in accordance to their script. The term comes from the 1998 movie, The Truman Show. Especially true when brought on by an occurrence similar to one in the movie itself.
If this happens too often see paranoia
SeaBass: Dude, I just had a Truman Show moment!
SquirrelMaster: How's that?
SeaBass: I was driving in my car, and on the radio they started talking about our small town, and they never do that!
SquirrelMaster: Maybe you should get that checked out.
SeaBass: My radio?
SquirrelMaster: No, your head...
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.