In fiction (comedic works especially), if a character is told to "act natural" to avoid drawing attention to what is supposed to be a covert task, there's a good chance they'll overdo it. Common flubs include reading a book upside down or Not So Innocent Whistling.
May be related to the Centipede's Dilemma, where a conscious attempt to do something is inexplicably harder than doing it unconsciously. Unrelated to Not Himself.
Acting Unnatural has been suggested to play 1 roles. Click below to see other actors suggested for each role, and vote for who you think would play the role best.