The seeds of truth do
hold the cure, but one must speak words true
Character Y suspects that character X has been lying, but Y can't prove it yet. Y may then alter the situation such that X will need
to come clean in order to avoid being in an even worse situation otherwise.
When it works out, it will have proven a lie. When subverted, character X may turn out to choose said worse outcome over coming clean anyway.
(Or alternatively, X might not have been lying after all.)
- The example from My Little Pony Friendship Is Magic linked to above.
- Cars 2 involves Mater making Axelrod admit to his part in the Allinol sabotage plan by driving up to Axelrod with a bomb for which him being able to deactivate it proves Mater's allegations correct, essentially forcing Axelrod to choose between coming clean or dying.
- In Friends, when Rachel finds out about Chandler and Monica, rather than simply telling one of them, "I know about the two of you," she takes an alternate route. Simply put, she attempts to steer a conversation with Monica so that MONICA will say that she's dating Chandler. Naturally, it fails.
- South Park: in the episode "My Future Self 'n' Me" Stan's parents have hired an actor to pretend to be Stan from the future whose life is ruined by drugs. Stan finds out the truth, and pretends to cut off his own hand to prove that Future!Stan isn't really him from the future. Stan's dad quickly cuts off the hand of the actor. "See?! It really is you!" But then Stan reveals he just pretended to cut his hand off.
- Done in Columbo - while investigating a murder in a Mensa club, Columbo confronts a suspect, telling him that he figured how the murder must have happened (a voice on a recording was used to fabricate an alibi). He makes the presentation and it does make sense ... and points to noone in particular - the villain could stay quiet and be safe. The thing is, it is not what really happened - Columbo consistently gets a key detail wrong. And the suspect's ocd won't let him ignore it...
- In Achewood, Little Nephew claims he is allergic to chicken so he won't have to eat Ray's cooking; Ray pretends to be concerned and fakes a phone call to the doctor, which details all the terrible things that will happen during the examination. Little Nephew's confession is only implied, however.
- Done several times in Mission Impossible. A notable example had a manufacturer of counterfeit meds who "suddenly" found himself in need of the real thing. Presented with a fake, he had to admit that he knew it was fake.
- The Brady Bunch Peter breaks Carol's vase while playing ball in the house. Peter's desperate not to get in trouble so he won't miss his camping trip. First, all the other kids confess to cover for him, and then Mike and Carol have Peter think up punishments for the others, hoping he'll feel so guilty, he'll confess. They also try rewarding him (as the only one who 'didn't break it' )to try and get a confession. It's the end of the ep before he feels bad enough to confess though.