Sometimes when a character is forced to make a vow, oath, promise, gesture, etc. they don't actually mean, they will cross their index and middle fingers in a way hidden to the character they're talking to but visible to the audience, to show they're actually lying. Most often the person will have their crossed fingers held behind their back, but off to the side, under a table, or somewhere else hidden is also possible.
Truth in Television, of course, which is the reason why it works as a visual cue, often in the form of An Insert. There's a number of guesses out there as to why it became a common gesture for lying, but the general idea is that it somehow either protects you from the consequences of lying or absolves you from being held to your word to begin with. In real life, this gesture is mainly used by children, especially since it's not a reasonable thing for an adult to do. Therefore, the trope is generally associated with characters who are very young or just act like they are.
It can also be used as an Out-of-Character Alert, both in-universe and Real Life, to signal to other people that a statement or gesture was made under coercion or otherwise insincerely. A simple example as such would be military prisoners of war being forced to participate in videos/photos either making it look like their captors was caring for them, or that the prisoners were renouncing their political beliefs. A discreet crossed finger or leg on film would be an indicator back home that the message was falsified in some way.
Not to be confused with visually similar "fingers crossed" used as "Good Luck" Gesture.
- In Reid Fleming, World's Toughest Milkman, Reid tells Mr. O'Clocke, "us bald guys gotta stick together". When Crabbe notices he has his fingers crossed behind his back and accuses him of lying, Reid admits that he's not actually bald. "I get my hair cut this way." Mr. O'Clocke finds that very flattering.
- When Superman and Spider-Man had an intercompany Crossover, Supes asked Spidey to turn himself over to the police after their adventure since he was wanted at the time. Spidey shook on it but had his fingers crossed behind his back.
- G'Nort's archenemy Scarlet Skier did it when granted a parole.
- At one point Deadpool's healing factor was breaking down, so him and his love interest Syrin decide to track down the Weapon X doctor who gave him his powers in the first place. Syrin makes Deadpool promise not to kill him when they find him. Deadpool tells her that he won't, to her relief. Then he reveals that—whoops!—had his fingers crossed! He runs away gleefully singing about how he's going to disembowel him, and Syrin tears off after him.
- Dexter's Laboratory: In comic book story "Salt and Pepper", Dexter and Dee Dee make a deal where she'll stay away from his lab forever. When he tries to collect, she reveals that she crossed her fingers.
- In The Land Before Time VI: Journey Through The Mists, after Littlefoot left with Ali to the Land of Mists, Littlefoot's grandparents warn Cera and the others not to go to the Land of Mists. Cera and the others do this while saying that they won't go there, but because Cera and Spike are both quadrupedal dinosaurs (a Triceratops and Stegosaurus, respectively), they do this with their hind feet, while Ducky and Petrie play this straight.
- Lock, Shock, and Barrel from The Nightmare Before Christmas do this after Jack Skellington tells them to leave Oogie Boogie out of their plot to capture Santa Claus.
- This was played with in Scooby-Doo! and the Reluctant Werewolf, where Dracula claims that he had his fangs crossed after promising to let Shaggy and friends go. And when he promises to turn Shaggy back into a human if he wins the race, his fangs really do cross!
- In the Disney short Ben And Me, Ben Franklin does this while shaking hands with his good friend, Amos Mouse, after promising not to play another trick on him, which led to Ben's famous discovery of electricity.
- Edgar does this when making a promise to Victor in Frankenweenie.
- In Meet the Robinsons, The Bowler Hat Guy finds Lewis and asks him to fix his memory scanner. Lewis agrees to do it if he promises to take him back in time to meet his birth mother. The Bowler Hat Guy promises while the viewer sees his fingers crossed behind his back. Later on, after the Bowler Hat Guy betrays Lewis after the memory scanner is fixed, Lewis calls him out on breaking his promise while Bowler Hat Guy responds, "Crossies! Doesn't count!"
- In The Truman Show, Truman's wife doing this covertly in their wedding picture tips him off to The Masquerade.
- In Willy Wonka & the Chocolate Factory, when Wonka gives the kids Everlasting Gobstoppers and makes them promise not to tell another living soul about them, Veruca crosses her fingers behind her back. In Julie Dawn Cole's memoir, she mentions that she did that in-character as Veruca, and the director wasn't familiar with the gesture and had to have it explained. Once he was told, he insisted on a close-up of it.
- In Sesame Street Presents: Follow That Bird, Ruthie and Floyd do this when Miss Finch asks them where Big Bird ran off to.
- In the film version of How the Grinch Stole Christmas!, the Grinch, after going back and forth on deciding to go to the Christmas party in Whoville, claims once and for all that he's going...but then reveals he had his fingers crossed on himself. He ends up going anyway when Max pulls a Trap Door cord that sends him to Whoville.
- The protagonist of Bavarian author Ludwig Thoma's Lausbubengeschichten does this with crossed fingers behind his back, after he played a prank on the village priest, who makes him swear an oath he didn't do it. He claims he learned this trick from his uncle, who's in the Bavarian parliament.
- The Night of Wishes: Early in the book, there's an illustration of Beelzebub and Tyrannia where Beelzebub does the finger cross behind his back and Tyrannia is implied to be doing the same. That was the first clue to their Chronic Backstabbing Disorder.
- At one point in Stephen King's Rage, the school-shooting protagonist is negotiating/toying with a school official over an intercom, and threatens to shoot one of his listening classmates if the official asks him any questions. As he says this, he holds up his crossed fingers for the viewers to see. And he means it; when the official finally slips up, the protagonist fires a shot into the floor.
- In his short story "At Loose Ends", the humorist Patrick McManus relates an instance where his childhood friend Crazy Eddie Muldoon was made to uncross his fingers when forced into a promise, so he crossed his toes instead.
- Lois & Clark: In the first season finale, Clark does this while telling Lois that when he said that he loved her (in the penultimate episode) he didn't mean it, he was lying to get her to not marry Lex.
- Referred to in Burn Notice, when Larry, the corrupt spy that Michael is temporarily forced to work with, kills the guy they're supposed to be kidnapping.
Michael: We had a deal!Larry: What can I say? I had my fingers crossed behind my back!
- Home and Away:
- One episode has Irene take Olivia with her to go on the run to prevent her evil grandmother from becoming her legal guardian. Barry catches up with Irene, tells her what she's doing is stupid, so they go back to her house where a meeting was meant to be taking place with the grandmother and a social worker. When they get back to the house, Irene comes up with a cover story that she went out shopping with Olivia and the car got a flat tyre. Olivia is asked if Irene's story is true and she nods. The viewer then sees her fingers are crossed behind her back.
- Another episode has Leah apologise to Ryan after falsely accusing him of wrecking her wedding dress. Ryan says that he accepts Leah's apology, but then we see he has his fingers crossed behind his back.
- Friends, the episode "The One Where No One Is Ready": Joey and Chandler are having a very long argument about who gets to sit on a chair.
Chandler: Well, Joey, I wrote a little song today. It's called: Get Up.Joey: All right! You can have the chair.Chandler: Really!Joey: Oh my, would you look at that! (holds up crossed fingers)
- Subverted in one episode of I Love Lucy. In it, Ricky forces Lucy to take a vow. Lucy, with one arm behind her back, begins saying the vow, but then Ricky pulls her arm out to reveal her crossed fingers, and separates them.
- In Rome, Vorenus' daughter Vorena (who thinks Vorenus killed her mother) makes the sign of the horns gesture behind her back when they're dining together. Vorenus used the same gesture when cursing his children after her wife killed herself and the way Vorena uses it basically means the same as if she had crossed her fingers: she doesn't mean any of the compliments she says to her father.
- Get a Life: Chris does this to Gus in the episode 1977 2000. Then he realizes he has no idea how to uncross his fingers, and consults a pull-down wall chart labeled "How to Cross and Uncross your Fingers" for step-by-step instructions.
- Mentioned on ER:
Kerry: Did you even take the Hippocratic Oath?Romano: I had my fingers crossed.
- In The A-Team episode "A Nice Place to visit", Amy makes the team promise they'll wait for her and keep out of trouble. They all promise with their fingers crossed with the exception of Murdock who forgets. He's reluctant to break his promise until BA drags him off with them. In a later episode "Sheriffs of Rivertown" BA has to swear on the Bible and tries to do so with his fingers crossed until Face catches him and emphasises it's the Bible.
- To Tell the Truth had a figure in its stage art of a man with his hand raised as if taking an oath, but he has his fingers crossed. It was used on the CBS and first syndicated series, then brought back for NBC's 1990-91 revival. The 2000-02 syndicated version had the crossed fingers in its logo.
- Episode "The Execution" of 'Allo 'Allo! uses the crossed fingers gesture, but the meaning is a bit ambiguous. Café owner and reluctant Resistance member René is about to be shot by Germans for blowing up the railway, but Colonel von Strohm and Captain Geering are entangled in it as well, so he was promised that the firing squad would use wooden bullets. Hans however brought two boxes to the execution: one with fake ones and one with real bullets. Lt. Gruber accidentally took both boxes. Nevertheless, Colonel and Captain smile at René and give him a supportive thumb-up. They are shown to have crossed fingers behind their back, meaning they either wish the plan worked or that they acknowledge their reassurance was not sincere.
- An episode of M*A*S*H had Hawkee lie on the radio to Quartermaster Corps, stating that the requisitions for additional blankets were in the mail. When Radar picked up said papers from the desk, Hawkeye held up crossed fingers.
- Subverted in Cousin Skeeter, where Bobby makes Skeeter promise not to say anything that would get Bobby in a crazy situation. Skeeter promises while the viewer sees him put his hand behind his back with his fingers crossed. Until Bobby angrily demands that he uncross his fingers and Skeeter pulls his hand out from behind his back and yelps to see his fingers are still crossed
- In Dragon Age II, a Lying Finger Cross shows up in the mood indicator whenever Hawke will lie with their answer.
- In DuckTales, a Lying Finger Cross is done by the blackhearted Flintheart Glomgold when Scrooge McDuck suggests a Teeth-Clenched Teamwork deal to retrieve Scrooge's Nephews and the previously earned treasures of the game from Magica De Spell. Glomgold would help get the kidnapped kids and Scrooge gives him the treasure as payment. Glomgold agrees to the deal with the fingers crossed behind his back, clearly willing to ditch the kids and Scrooge if he gets his hands on the treasures first.
- Played with on SpongeBob SquarePants. When SpongeBob and Patrick promise Mr. Krabs not to play on the fishing hooks, Patrick claims he had his fingers crossed. SpongeBob then points out that he has no fingers.
- In an episode of The Adventures of Super Mario Bros. 3, King Koopa crosses his fingers when he promises Crimewave Clyde half of what the Koopa Kids steal as a reward for teaching them how to commit crimes. Clyde doesn't catch on until it's too late but he makes them pay with the help of the Mario Bros.
- The Joker from The Batman does this in an episode when making a deal with his nano-tech clone—who does it as well. No points for guessing how the deal went.
- An episode of Make Way for Noddy has Dinah Doll tell Gobbo that she knows he's lying because his fingers are crossed, and that goblins cross their fingers when they lie.
- In The Simpsons episode "Lisa's Wedding," when Lisa and Marge talk through a video phone:
Lisa: Mom, remember when I was little, we'd always planned my dream wedding and you always promised to... you know, well, keep Dad from ruining it?Marge: [crossing her fingers] Oh, don't worry, honey, I guarantee your father will behave.Lisa: Mom, it's a picture phone.Marge: [looking at her fingers] What? This? Oh, no, I've just got a touch of the rheumatiz.Lisa: Oh, OK.Marge: [Whew gesture]Lisa: Mom, picture phone.
- In the Gravity Falls episode "Fight Fighters", Mabel makes a promise to Grunkle Stan and puts on a sweater with a hand doing the "Scout's honor" gesture on the front. When she turns her back to the fourth wall we see the back of her sweater has a hand with its fingers crossed.
- In "Scary-oke", Dipper and Stan do this to each other when they make a deal that Dipper only use his journal for self defense against Gravity Fall's supernatural side and not look for trouble only if Stan, who had just revealed that he had been faking being oblivious to the town's weirdness all this time, doesn't have any other bombshell secrets he's keeping, the audience knowing about the machine he has in the basement.
- In "Northwest Mansion Mystery", Pacifica looks at pantings of her ancestors showing them to be lying, cheating scoundrels, one of whom is a Calvary captain signing a peace treaty with an Indian chief while doing the cross behind his back.
- Hermes on Futurama crossed two digits of his new extensible robot-arm when he promised he wouldn't get any more cybernetic upgrades.
- The Mask: Peggy tried this in the very first episode but Stanley caught on.
- Kissy Fur: In one episode, Lenny constantly bullied other kids for their lunches. Near the end, he saw himself in a pinch where he needed their help and they only agreed when he promised he'd no longer bully them. The next day, he broke his promised and, when called out on it, he claimed he had his fingers crossed when he made it. Fortunately, they'd learned how to use the strength of numbers against him.
- In the Warners' cartoon Sniffles Bells The Cat, the end scene has Sniffles the mouse launch into a tremendous epic of how he demanded the local cat wear the bell he had, going into details even as the viewers see how he's got two sets of fingers crossed behind his back.
- Jem: Techrat did it while telling the Misfits how "safe" his gimmick in "The Jem Jam - Part 2" was.
- In the first Valentine's Day Episode of Ed, Edd n Eddy, Marie and Lee cross their fingers behind their backs while promising May a gorgeous makeover.
- In Brandy & Mr. Whiskers, Mr. Whiskers promises Brandy he won't interfere with Ed's attempts to ask Lola out by showing her that his fingers, ears, and toes aren't crossed. However, after Brandy leaves, he crosses his teeth while doing an Evil Laugh.
- At the end of the Camp Lazlo episode "Dirt Nappers", after Camp Kidney gets their diet back, Sampson promises not to use his vacuum cleaner again. As he and Lazlo walk into the sunset, we see him crossing his fingers with one hand and holding his vacuum in the other.
- Plastic Man and his sidekick, Woozy, do this on one episode of Batman: The Brave and the Bold.
- In the Beetlejuice episode "Out Of My Mind," Beetlejuice promises Lydia he won't prank her dad. But naturally, he had his fingers crossed behind his back.
- He-Man and the Masters of the Universe (1983): Orko did this in "Disappearing Act" when he promised He-Man, Man-At-Arms and Battlecat he'd clean up his room without magic.
- In "Dree Elle's Return", Dree Elle's brother did this when he promised her he'd not play pranks during their stay in Eternia.
- The Grim Adventures of Billy & Mandy: In the Martian (zombies saying "cow pies" near the end) episode, the Martian leader crosses his fingers behind his back.
- In the Aqua Something You Know Whatever episode "Bookie" Master Shake tried using this to welch out of paying a bet. He promptly gets his fingers broken by the mobsters running the gambling ring.
- In the final episode of Daria, Kevin reveals to his girlfriend Brittany that he flunked his senior year and won't be graduating with her. He still gets her to promise that they'll stay together while she's in college, but she nervously crosses her fingers behind her back.
- Peter Pan & the Pirates has Captain Hook of all people pull this off. After giving his word and then breaking it, Wendy calls him out on it, saying that "You swore an oath as a gentleman!" Hook then calmly states that while he swore his oath as a gentleman, he had his fingers crossed as a pirate.
- In the My Little Pony: Friendship is Magic episode, "Princess Spike", Spike tells Princess Cadence that he's using Twilight's authority to improve the summit. Then we see that he's crossing his claws behind his back.
- In the Wacky Races (2017) episode "Cold Rush", Peter Perfect makes Dick Dastardly promise that he won't cheat in the race this time. To make sure he's not trying anything funny, Peter also makes Dick stop crossing his fingers and his toes.
- In Transformers Animated episode "Velocity", Bumblebee asks Bulkhead to give him his turbo boosters back so he can find out who the blue racer is. Bulkhead tells him to promise not to go any shenanigans, with Bumblebee saying so while crossing his fingers.