If you're a spy, working undercover, and none of the viewers know this yet, your performance will be flawless and thorough. However, as soon as the audience knows your secret (or if they know from the start), everything you say will sound utterly unconvincing, your facial expressions will display the exact opposite emotion from the one you're trying to fake, and you will constantly make furtive glances about your surroundings whilst doing even the simplest of tasks. Yet somehow, none of the people you're trying to deceive will notice this.