Sometimes it's really hard to convince someone of what you're saying. Perhaps you're addicted to Crying Wolf so when you do pierce the Masquerade your credibility is gone. Or maybe Muggles see anything so weird and out of the ordinary such an affront to their sensibilities they automatically disbelieve you, leaving the likes of Jor-El and Cassandra desperately saying "You Have to Believe Me!!"
This is not one of those times. This time they believe you.
Usually in this case, the main reason someone believes you is because your story sounds so crazy compared to what you would usually say. Either you're in good standing with the Reasonable Authority Figure so they'll at least hear you out, or even if you cry wolf all the time the nature of this crazy story is so out of hoc with your usual lies that they at least listen to you. Other factors can be at work here such as the Powers of Trust, Friendship or Love, leaving one more likely to believe the story but perhaps say "If you were any other man I'd call you crazy." The baseline for this trope is that it's usually a story that sounds completely made up to the average listener, but is actually true.
- In Death Note, Mello tells Near about the existence of Shinigami and how they're connected to the Death Note. Near's SPK allies scoff, but Near believes him on the logic that if Mello really was lying to mislead them, he'd never make up such a ridiculous-sounding story to do it. The fact there's a magic notebook that kills people presumably helps open his mind to the possibility.
- In the Ultimate Spider-Man - Marvel Universe Spider-Man Milestone Celebration Crossover Spider-Men, Peter Parker-616 tries to explain the Alternate Universe and other mechanics that are involved in this crossover to Nick Fury and The Ultimates. Fury' immediately believes Peter's story because nobody would be crazy enough to make that up.
- Rorschach in Watchmen believes Moloch when he tells him how the Comedian while desperate and crying, paid him a visit at night.
Rorschach: Funny story. Sounds unbelievable. Probably true.
- In The Pulse, Ben Urich gets a call from a source inside S.H.I.E.L.D. about Nick Fury's recent actions and how they tie into the attempt on Luke Cage and Jessica Jones' lives. Jonah believes him as soon as the pieces fall into place.
- Towards the end of Superior Spider-Man Peter is finally back in his own body after being body-swapped with Otto Octavius for about thirty issues. This is Spider-Man 2099's reaction when Peter sums up the events for him.
Peter: I was brain-swapped with Doc Ock, so I don't know what's happening... but I'm off to fight the Green Goblin and I could use some help.Miguel: Yeah, that sounds just stupid enough to be right. Let's go.
- The Stargate SG-1/Buffy the Vampire Slayer fic "Scattered Hearts" basically uses this when Daniel Jackson has to convince General Hammond why he's allowing Dawn Summers to stay with him on such minimal evidence that she is his daughter's adopted sister (Daniel conceived Buffy with another girl in foster care when he was a teenager) when she could be a plant by the NID. As Daniel explains, it's extremely unlikely that anyone would realise that he was Buffy's father when so many people at the time believed that her father was the foster father of the girl in question, to the extent that it took Daniel years to be sure of the connection even when he knew what to look for. Finally, Daniel points that even if anyone put the facts together to identify him as the father, it would make more sense for an NID operative to pose as Buffy herself after her death rather than send in an operative to pose as Buffy's sister.
- In Fantastic Beasts and Where to Find Them, when Newt Scamander ropes Jacob Kowalski into the magical world, the latter immediately believes that it's all real as he hasn't the brains to make any of it up.
- In Baby Driver, when the other members of the Caper Crew confront Baby about him sneaking off at 2 AM, and finding his tape recorder containing records of their criminal conversations, Baby admits, honestly, that he remixes the conversations into music. Bats points out that this is a really fucking stupid excuse, and Buddy goes further, saying the excuse is so fucking stupid, the cops would never think to come up with it.
- In Superman, when Lex Luthor, the self-proclaimed Greatest Criminal Mind of Our Time hears early news reports of a flying "Superman" acting as a hero, one of his associates wonders if the stories are real and he declares that they must be — because "if anyone was going to perpetrate such a fantastic hoax, it would've been ME!"
- The Andromeda Strain: When General Mancheck tells Team Wildfire about the origin of the Scoop satellite contents coming from investigating a wormhole before crashing on Earth. The team is skeptical but Stone believes it because "It's too fantastical to be a lie".
- The Andy Griffith Show: Opie tells his Paw about a man so ridiculously crazy — walking atop trees, jingling as he strides, blowing smoke from his ears, carrying 12 extra hands on his belt, and wearing a big, shiny silver hat — that it's hard to believe "Mr. McBeevee" is a real person. (McBeevee, in fact, is a real person, a telephone lineman whom Opie has made friends with.) But when McBeevee gives Opie a quarter and excitedly shares this with his Paw, Andy immediately suspects that he stole the quarter and immediately tells him to say that McBeevee is an imaginary friend, or else he'll get a whipping. Opie tries to concede to Andy, but chokes up and tells him that McBeevee is real ... and amazingly, Andy relents. And yes, in the end, Andy does learn (by chance) that McBeevee is real.
- On The Brady Bunch, someone sends Jan a locket anonymously, and the only clue to his/her identity is that the enclosed note was written on a typewriter where the 'e' was slightly off. Suspecting Mike, Carol takes Alice and sneaks into his office to test his typewriter, only to be caught by the security guard. He concludes that it's not the kind of excuse a burglar would cook up.
- In the series finale of Sense8, Kala's husband Rajan believes the cluster and their allies when let in on the sensate conspiracy, because all these international strangers wouldn't be hanging around and acting as they were if it were a lie.
- In Snuff, Sam Vimes comes running to his wife Sybil, babbling about the beautiful music being played by the goblin girl Tears-of-the-Mushroom. Sybil at first expresses her disbelief, before- in the same sentence- realizing that if Vimes, who habitually falls asleep from boredom at music recitals and the opera, thinks it's that good, then... "You know what? You've convinced me."
- In The Lion, the Witch, and the Wardrobe, this is the logic that the Professor uses to declare that Lucy's story about a magical realm in the wardrobe is actually true: she claimed to have been gone for hours, yet only seconds had passed. If she were really making it up, she would have remained hidden for some time before attempting such a story, and a girl Lucy's age is unlikely to make up such a story (Of course, in other books we find out that the Professor has been to Narnia himself, and the wood used to make the wardrobe actually came from a tree in Narnia, so he wouldn't be surprised to find that the wardrobe had magical properties).
- The Unbelievable Truth: Used often, with panelists getting buzzed because their answers are so crazy they must be true, like the one about an Indian man marrying a pet. Henning Wehn buzzes in because he figures no-one would get away with saying that on BBC Radio 4 otherwise. Of course, since the point of the game is to hide lies as truth, oftentimes panelists will get caught out on this principle as well.
- In Pillars of Eternity, one questline has you retrieving an ancient text that was stolen from the Hall of Revealed Mysteries, a temple to the eccentric god of secrets, Wael. When you actually get the text from the thieves who stole it, Wael will personally instruct you to bury it in a particular location just so people can continue to go hunting for it and eventually rediscover it. If you do this and tell the story to in total honesty to the quest giver, she will refuse to believe you (forfeiting any material reward, though you still get the XP)... unless you have a high Honest reputation, in which case she'll note that normally she wouldn't believe such a yarn, your reputation and the fact that doing something so bizarre and arbitrary is entirely within Wael's nature is enough for her to take your word for it and gives the promised reward.
- This is Varric's comment about Cullen's anecdote during the game of Wicked Grace in Dragon Age: Inquisition. He tells the other players a story about his Templar days, and while everyone laughs, a few of them suggest that maybe he's exaggerating. Varric replies that "That's how you know it's true! I could never put that in one of my books - too unlikely."
- In Spoony's Counter Monkey stories, he recounts the story of a player who could never arrive at the agreed-upon time. On one occasion Spoony called him to see where he was, and the player said he had to head back to his house because he forgot his pants. After a moment's thought Spoony decided he must be telling the truth because nobody would use such a lie to excuse being late.
- The Simpsons:
- Lisa uncovers evidence that the town founder, Jebediah Springfield, has been whitewashed throughout the centuries and was actually a bloodthirsty pirate and rogue. Most of the town scoff, but Homer believes her because she's smart and insightful and usually right about these things, even if they sound crazy.
- In another episode, after Skinner and Krabapple fall in love, rumors spread that they had sex in a broom closet. Skinner silences these stories by confessing in public that he is a virgin. This satisfies the public, and Superintendent Chalmers notes that nobody would lie about being a virgin. The ending subverts this however, as Skinner reveals he lied.
- Garfield and Friends: The satire that revealed such crazy facts as there being no Wyoming and that bowling bawls are shrunk to create raisins were so crazy "It Must Be True." But when Garfield (the show's host) claims the crazy fact that dogs are stupid, the audience — consisting entirely of dogs — doesn't think it's so crazy, or funny, and go after the feline.
- Futurama: When Bender goes to the Fortune-Telling Robot for help with his werecar curse, Fry dismisses her answer as ridiculous. She retorts it's so ridiculous it must be true.