The gist of the trope is when a character in a mentally vulnerable state similar to sleep (usually actually sleeping) when another character whispers in his ear in the attempt in order to influence the sleeper's dreams or thoughts.
- Pleasant: The whispering character says something pleasant which makes the sleeper feel reassured or calmed, maybe even delighted.
- Troubling: The whispering character attempts to trouble the sleeper's dream by plaguing his/her mind with troublesome thoughts and worries.
- Command: The whispering character chants some sort of command or mantra so as to subliminally influence the sleeper's behavior when they wake up.
For example: Alice and Bob are sharing the same bed, and Bob wakes up when he overhears Alice's muttering in her sleep due to a bad dream, visibly upset. Bob tries to whisper in her ear some sort of encouraging message or mantra for which to calm Alice down while she is completely unaware of Bob doing this.
Compare Crashing Dreams (that's about dreams and real life coinciding, like dreaming you're kissing someone while being licked by your dog in real life, this is a Mind Control trope about manipulation by suggestions given to a sleeping subject) as well as Sleep Learning and Subliminal Seduction.
- Oruchuban Ebichu: Ebichu does both Pleasant and Troubling. He does Pleasant to her beloved master (normally depressed and desperate "Christmas Cake") who ends up waking up the next morning feeling completely refreshed and in good spirit. Soon after, she tries to do Troubling to said's master undesirable boyfriend by pretending to be the boyfriend's boss at work and calling him useless and all that. This attempt is subverted by the fact that the target was actually awake the entire time and hiliariously beats Ebichu bloody.
- Kenichi: The Mightiest Disciple: Kenichi's martial artists masters use the Command version of this in the attempt to convince Kenichi to accept the Training from Hell they want to give him to prepare for an opponent he was having trouble with. The actual attempt doesn't work though.
- In Slayers Perfect (Slayers the Motion Picture), it's played for laughs as Lina awakens and sees the King and the Queen chanting too loudly at her. The laughs are made even more potent by the fact that Lina already has mysterious dreams, but this one turns to be a fake.
- One episode of Kirby: Right Back at Ya! had King Dedede giving out pillows to everybody in Cappy Town supposedly in an act of good will. But in reality, they give you nightmares about Kirby and make you hate him.
- Another episode had King Dedede selling Dedede Dolls to the townspeople. Then every night, the dolls would convince the cappies in their sleep that they like King Dedede and that they would give all of their money into the dolls, so that Dedede could use the money to pay off Nightmare Enterprises.
- Momoko tries this twice on Koushi in Sumomo Mo Momo Mo. The first time, she inadvertently wakes him up and dramatically creeps him out. The second time, she replaces his educational tapes with phrases that she wants him to say to her. The hilarity ensues when Iroha chooses that night to try to assassinate Koushi. He somehow dodges an expert ninja in his sleep, restrains her, and then repeats the lines that Momoko recorded... several of which were blatant and lewd requests for sex. Iroha, not realizing why Koushi said those, instantly undergoes a HeelFace Turn and becomes a romantic rival to Momoko.
- Kaguya tries to pull this on Shirogane in chapter 10 of Kaguya-sama: Love Is War, whispering that she loves him in order to get him to admit his feelings for her (although Fujiwara barges in before she can say it and it's revealed at the end of the chapter that he was only pretending to be asleep in an attempt to manipulate her). A similar scene would pop up 134 chapters later, the key difference being that neither of them were pretending.
- Demon Slayer: Kimetsu no Yaiba: Urokodaki repeatedly told a demon-turned Nezuko to protect and care for humans during the two years that she slept through while Tanjiro was training, to strengthen her already unusual resistance to eating humans. Tanjiro wasn't very happy about this as he felt it was like brainwashing, but felt better after Nezuko proved she alone would decide who to protect.
- In The Life and Times of Scrooge McDuck: The Dream of a Lifetime, the Beagle Boys have used one of Gyro Gearloose's inventions to invade Scrooge's dreams to acquire the combination to his vault, and Donald is sent in to stop them. The triplets weaponize this trope to help Donald and Scrooge from the outside, though all of their attempts fail: banging mugs together to sound like horses galloping makes it rain mugs in the dream instead of making horses appear, and making banging sounds to summon a gun instead summons a drumset. They finally succeed when they use the smell of Scrooge's Goose Egg Nugget, which makes him start dreaming about his days as the King of the Klondike...
- Gaston Lagaffe: Fantasio and Spirou sneak up on Gaston as he's sleeping. Fantasio then whispers into Gaston's ear to demonstrate his basic philosophy: "eat": big grin, "work": big frown, "sleep": big grin... Then Spirou whispers "Fantasio": big grin and happy sounds.
- The Powerpuff Girls: In "Micro Managing" (DC issue #68), the Micro-Puffs (three troublemaking sprite avatars of the girls) brainwash Bubbles and Buttercup in their sleep into thinking she is the leader of the Powerpuffs. It doesn't work on Blossom as she's already the leader. When Bubbles' and Buttercup's Napoleon complexes don't subside, Blossom seeks help from Mojo Jojo in turning the tide.
- In The Unknown Supergirl, Lesla-Lar brainwashes Supergirl in her sleep into believing she is Lesla herself in order to replace her.
- The Girl with the X-Ray Mind: As Lena Thorul is sleeping, she is kidnapped and brainwashed by villain Lesla-Lar into believing she is the Kandorian mad scientist.
Lesla-Lar: My brain-washing helmet will erase Lena's memories and replace them with selected details of my life here on Kandor! When she awakens she'll believe she's me!
- Calvin from Calvin and Hobbes does this to Hobbes with the use of a cookie◊.
- In Bloom County:
- Opus tries to get in to see Steve Dallas after an operation. He is refused because the doctor is "debriefing" the patient.
Dr. LeGrunt: You will not sue. You will not sue. You will not sue. You...
- In another series of strips, the boarding house's resident cockroach uses this tactic to get people to start leaving out food for him.
- Opus tries to get in to see Steve Dallas after an operation. He is refused because the doctor is "debriefing" the patient.
- The Command version was a recurring gag in Outland, with Milquetoast the Cockroach whispering in people's ears as they slept. Opus was usually the recipient, but one strip was all about celebrities' crazy decisions being influenced by behind-the-scenes whispering cockroaches.
- Foxtrot has one where Jason tries to convince his mother to increase his allowance by getting her to dream of all the ridiculously expensive stuff he's buying for her.
- In one Drabble strip, Norman whispers into his sleeping father's ear "You will buy Norman a Trans-Am. You will buy Norman a Trans-Am." The second panel, set the following day, shows his father presenting him with a canned ham. Norman then thinks he has to learn to enunciate.
- In one Dilbert strip, the PHB did this to a higher up to try an increase his department's budget while Wally tried to whisper a command for the higher up to kill the PHB.
- Blondie strip for July 12th 2014. While Dagwood is sleeping on a couch, neighborhood kid Elmo Tuttle whispers "Just wanted to wish you a restful and happy Hot Dog Month" in his ear. When Dagwood wakes up he has a hot dog cookout. Elmo is shown eating one and calling himself a "career button-pusher".
- A fairly common occurrence in Garfield. One particularly noteworthy example had Garfield's alarm clock describing him wandering through a pasta factory and coming across a gigantic lasagna, before loudly waking him up just as Garfield was about to dig in.
Garfield: I'm a light sleeper~
- Another strip had a spider trying to do this to ensure Garfield wouldn't squish him. It didn't work.
- In one The Far Side strip, a dog whispers through a crack in the window to their sleeping owner to put the cat out so that it can attack the cat. Made even better because the cat is awake and watching the dog do this.
- On Dumbo, Timothy whispers in the ringmaster's ear while he's sleeping to plant the idea of using Dumbo on the elephant pyramid routine.
- In Rudolph the Red-Nosed Reindeer (1998), Slyly is pickpocketing the Big Bad when she blearily asks what's going on. Slyly tells her to go back to sleep, which she does.
- On Her Majesty's Secret Service: Blofeld is using this to brainwash the women at his clinic, so he can use them as couriers for the deadly virus he's developing.
- In The Sixth Sense, the protagonist does this to his wife in the end.
- Darby O'Gill and the Little People: While Michael McBride and Katy O'Gill are asleep, King Brian talks to them to influence them into falling in love with each other.
- The villain of the first Hellboy movie did this to Liz, resulting in Liz burning the entire asylum.
- Muppets from Space: Pepe and Rizzo use this and a fan to get Gonzo to build a jacuzzi.
"Build a jacuzzi and they will come..."
- Inception takes this to its logical end: literally invading someone's dream to plant an idea deep in his subconscious. In theory this shouldn't work, but the protagonist knows otherwise because he's seen it happen in practice.
- In Brave New World, this effect is called Hypnopaedia. A combination of Pleasant, Troubling and Command (especially Troubling and Command) is used to condition children according to their place in the caste system. One of the protagonists, Bernard Marx, is actually one of the writers behind the hypnopaedia, and takes a perverse pleasure of saying, when someone says one of the aphorisms learned through it, exactly which ages they heard that hypnopaedia.
- In The Centauri Trilogy (novels in Babylon 5's Expanded Universe), while Emperor Londo has a Drakh Keeper controlling him, the Drakh used a more benign (less coercive) variation of a Keeper known as a "Dreamweaver" to implant dreams in Minister (and eventual Prime Minister) Durla during his sleep, encouraging and guiding his ambitions for empire that the Drakh planned to use with the Centauri.
- Uplift: Gailet Jones is the victim of this at the hands of the Gubru, without her knowledge. She doesn't realise what's happened until she finds herself unable to object to the highly improper Gubru-manipulated uplift ceremony that would make Neo-Chimps their clients.
- The War With Mr. Wizzle by Gordon Korman. The girl students try to change the behaviour of teacher Gloria Peabody by playing tapes telling her to be nice while she sleeps. Unfortunately they just make Peabody even crankier because she's not sleeping properly.
- Star Wars: Phasma reveals that First Order stormtroopers start their brainwashing as children, listening to propaganda as they sleep. Creepily enough, they're fully aware of this and find it comforting, as it's the closest they have to a mother figure. Cardinal even compares it to a lullaby.
- Friends: In the episode "The One with the Hypnosis Tape," Chandler uses a self-help stop-smoking tape given to him by Rachel to listen to while he sleeps, unknowingly affecting more of his behavior than just the quitting smoking part, because the tape has messages such as "You are a strong, confident woman who does not need to smoke." Joey learns of the tapes and in a Command usage of this trope, adds his own words to the tape in an attempt to influence Chandler in other ways...
Joey (in monotone, on the tape): Joey is your best friend... You want to make him a cheese sandwich every day... You also want to buy him hundreds of dollars of pants...
- An episode of Hannah Montana used Command when Lilly and Oliver had discovered that Miley's boyfriend was cheating on her, and Lilly tried doing this to encourage Miley to break up with him.
- Liv and Maddie: This was part of the Twist Ending of "Helgaween-A-Rooney". The entire episode was just a dream Maddie had when Karen hypnotized her into not worrying about her buckled knee.
- The Doctor Who story "The Macra Terror" features the villains trying this on the Doctor and his companions, mixed with a bit of pheromones for added effect, but only ends up affecting Ben.
- One episode of Salute Your Shorts had Budnick telling a ghost story about Zeke the Plumber, a custodian who was killed in a gas explosion. The gist of the story is that whoever touches his plunger will be haunted by them in their dreams, and since Telly was one of them, she has a sleepless night which causes her to nod off in the mess hall, after which Budnick comes up and starts whispering in her ear, "Zeke the Plumber, Zeke the Plumber..." Guess who she starts dreaming about?
- In an episode of Jonas, Kevin becomes addicted to Nick's cookies and keeps insinting on more. When Nick refuses to bake him anymore cookies, Kevin tries to brainwash him by murmuring to him in his sleep. It seemingly works, but it is then subverted as Nick was actually awake that night and baked the cookies on purpose to teach Kevin a lesson (justified that Kevin was having a Sugar Rush as a result of eating too many cookies).
- Subverted in one Midsomer Murders, when a suspect reports dreams of a voice telling her "kill that man", also revealing that she's prone to sleepwalking. This, along with Barnaby reading an article of a man acquitted of murder while sleepwalking and finding a hidden loudspeaker system in her room, leads the viewer to think she did it. However, it turns out the murders were committed by another guy who killed the victims almost on impulse (the loudspeakers were there for gaslighting purposes).
- Done inadvertently by Keith in one episode of The Partridge Family. He stayed up all night working on a song. In the morning, Danny (who sleeps in the room next door) announced that a new song came to him in a dream. Danny ended up getting credit for writing the song, while Keith's attempts at explaining what really happened were interpreted by the other characters as jealousy.
- Jonathan Creek: The solution to "The Eyes of Tiresias" hinges on this, with an old woman hearing details of a planned murder that had been recorded on to a CD that played while she slept, causing her to have what she believed was a prophetic dream about the coming murder.
- Done with sleep education in one episode of Round the Twist, leading to all sorts of nonsense: for example, at one point Bronson creates some interesting delusions by reading a superhero comic out loud.
- Mork & Mindy: As part of his attempts to convince Mindy to marry him, Mork sneaks a tape player into her room while she's asleep which plays the message "You will marry Mork. You love Mork. Mork loves you". Mindy immediately wakes up and turns the player off.
- When Eric needs to quickly learn to ice skate in Boy Meets World, Jack gifts him a tape to play while he's sleeping. Jack's mother had used it to lose weight, and Jack dubbed over a few words (soothing female voice "You are a strong, confident woman who can" Jack's voice "ICE SKATE.") Somehow, it actually works.
- In a The Whitest Kids U' Know sketch, three guy see a co-worker sleeping, and they decide to prank him by telling him in his sleep he's falling from the sky, and after telling him he's going to crash into the ground, his head explodes. They realize that they some kind of Reality Warper powers involving sleep suggestions, so they have one of them fall asleep and suggest to him he robbed a bank with millions of dollars. It doesn't work. All they seem to be capable of is making sleeping people's head explode.
- Tales from Muppetland: The Frog Prince: After Robin is captured by the witch Taminella, Kermit tries to trick Sweetums into freeing Robin by imitating Taminella's voice while Sweetums is sleeping and ordering him to "stay asleep let frog go." It almost works, but then backfires.
- In the Fraggle Rock episode "The Trash Heap Doesn't Live Here Anymore," Wembley whispers into a sleeping Junior Gorg's ear, getting him to sleepwalk and move the Trash Heap to another part of the garden instead of throwing her in the river.
- One episode of Feral TV has Derryn the dog start using sleep education tapes, at which point the others start sabotaging him by substituting other tapes. They get stopped before they can use 101 Uses for a Dead Cane Toad, much to the relief of their cane toad boss.
- Fire Emblem Fates: Selena whispers in Odin's ear while he sleeps in their S support. She just wants to get back at him for using a spell to manipulate her dreams, but after he wakes up, he proposes. It turns out he was awake the whole time, but he really has fallen in love with her, and she accepts his proposal.
- Episode 6 of RWBY Chibi Season 2 has Ruby do this to Weiss. Not only does it work, it's later revealed she did this to Yang and Blake!
- In the Homestar Runner short "A Jorb Well Done", Strong Sad's attempt to cure Coach Z's inability to say the word "job" is to effectively play a recording of him saying "job" properly 285,194 times while Coach Z sleeps. It works... at the expense of Coach Z able to say Homestar's name.
- A variation of this happens, albeit accidentally, in an episode of Dexter's Laboratory. Dexter goes to bed wearing a device on his head that plays a vinyl record, so as to teach him French lessons as he sleeps. However, the record skips and repeats "Omelette du Fromage" (cheese omelet) all night, and that ends up being the only thing he's able to say for the rest of the episode.
- Wilma and Betty tried this on Fred and Barney on The Flintstones to make them buy them everything they want. When Fred and Barney finally catch up on what's going on, they flip this around on the girls by pretending that it's Gone Horribly Right and they are stealing stuff in a hypnotic daze.
- The Garfield and Friends episode "Jukebox Jon" had Jon trying to hypnotize himself in his sleep into not biting his nails with help of a special device in order to appeal himself to a comic book executive who despises said habit. However, it backfires when Garfield accidentally breaks the record that was playing on the device, so he substitutes it with some "Learn to Speak Spanish" records, records of 50's doo wop music, and cartoon sound effects instead. Hilarity Ensues.
- The Simpsons:
- The episode "Duffless" opens with Principal Skinner awarding Bart first prize at the school science fair. The phrase "first prize" echoes until the scene transitions to reveal that Lisa was saying this into Bart's ear while he was dreaming because she was "just screwing with [his] mind."
- In the episode "Bart's Friend Falls in Love", a side plot has Marge buying Homer subliminal sleep-learning tapes on weight loss. However, they're all out of them, so the company sends him a vocabulary-building tape instead, and Homer becomes superlatively verbose. When he gets on the scale one day and realizes he's gained weight, he throws the tape out, and before long, he can't even remember basic words like 'spoon'.
- And Played for Laughs at the end of "Half-Decent Proposal", where Artie sends Marge a gift that's supposed to help her sleep through Homer's snoring.
- In Adventure Time, "Ignition Point", after Finn and Jake retrieves Flame Princess' scented candle from the Fire Kingdom, they give it back to her while she's sleeping and lit the candles with her hair. Her father, Flame King, appears and starts whispering "evil" into her ear to make such she remain evil after discovering Finn wants to convert her to good. But Flame Princess wakes up surprising him and herself and he quits for now.
- Kid vs. Kat: In "I'm Okay, You're a Kat", Coop discovers a self-help tape in the House of Swap and uses it to make himself far more cheerful by playing it while he's sleeping. Kat gets annoyed by how Coop's optimism makes it much harder to annoy him and edits the tape to make Coop pessimistic, making him scared of his own shadow and literally cry over spilled milk. Afterwards, Kat uses another self-help tape on Burt to brainwash him into his servant. When Coop finds out, he decides to use a self-help tape to become a tough guy, which turns him into a thug and he almost drops his entire family in a pool of electric eels before he is snapped out of it.
- In Scooby-Doo! Mystery Incorporated, the culprit disguises himself as the Dreamweaver in order to manipulate his victims in their sleep to do criminal acts in order to have them arrested or be humiliated in public.
- SpongeBob SquarePants:
- In "Fear of a Krabby Patty", SpongeBob needs therapy after hallucinating of Krabby Patties. The psychiatrist hypnotized SpongeBob to sleep and goes on to do this. Being Plankton in disguise, he subliminally tries to tell SpongeBob to explain the recipe of Krabby Patty. But it fails, since SpongeBob instead gets a dream where he regains his resolve to make patties again.
- At one point in "Survival of the Idiots", when Sandy is dreaming about Texas outlaws in her hibernation, Spongebob and Patrick (who really aren't supposed to be there) pretend to be said outlaws and tempt her to chase them in her sleep.
- In The Smurfs (1981) episode "Papa's Flying Bed", Papa Smurf's new bed causes whoever sleeps in it to be transported to wherever it is they are dreaming about. After the bed takes Papa Smurf, Brainy, Clumsy, and Baby to a pirate ship and then a child's bedroom with toys, it ends up traveling to Gargamel's lair when Clumsy dreams of being taken there. Papa Smurf whispers in Clumsy's ear to dream about his home in the Smurf Village with his beautiful rock collection, and soon enough Clumsy's dreaming takes them away from Gargamel before he gets their hands on them and straight into Clumsy's house.
- The Loud House: In "Driving Miss Hazy", Lori tries to sabotage Leni's driving test by planting headphones playing a tape with bad driving instructions on her head while she's asleep. Lincoln calls Lori out, telling her that not only is she being selfish, but her bad driving instructions could get Leni hurt.
- The subliminal audio tapes described above in the entry on The Simpsons are a real thing, and indeed, one of the most popular applications for them is weight loss. Their efficacy is mixed.