First night in a strange place? Warm milk! Can't sleep? Warm milk! Character has a nightmare? Warm milk!
The idea of warm milk being a perfect sleeping aid is Older Than Feudalism, and can be found in most cultures that have milk-producing animals.
This can be Truth in Television, medically speaking. Milk has opiate precursors in it, which is part of the reason why it tends to be a go-to sleep aid for some people, especially since heating the milk seems to help make said opiates a little more effective. It also contains the amino acid tryptophan which has a relaxing and calming effect. However, its effectiveness can greatly vary from person to person. There's also the fact that it's high in fat, protein and carbs, meaning that it can make someone sleepy in the same way any large meal can.
Subtrope of Comfort Food. A very likely trope to show up in an Insomnia Episode. A character who offers warm milk is frequently established as a caregiver type, if not a Parental Substitute. It can also be used to deliberately sedate another person.
- In an Ernest P. Worrell commercial, Ernest wakes Vern up in the middle of the night to tell Vern he can't sleep, and asks to borrow a glass of milk to help him sleep, pointing out that milk contains calcium, minerals, vitamins, "and none of that caffeine to keep ya awake all night."
- There's a brand in Ireland called Lullaby Milk which is advertised as being more effective for this than normal milk.
- Inverted in Magical Girl Lyrical Nanoha A's, where Hayate gives Signum some warm milk to help her wake up rather than fall asleep. It also serves as a rather effective metaphor for the overall feeling of the Yagami household.
- In JoJo's Bizarre Adventure: Diamond is Unbreakable, Yoshikage Kira mentions drinking warm milk before bed every night to help him sleep during his monologue about living a quiet life.
- Bloom County: In a Sunday strip shortly before the 2004 presidential election, Opus calls on a rental grandmother to care for and comfort him on election night. When the grandmother arrives, he was heating up a glass of milk to help calm him down, and offers her a glass as well (though she requests warm tea with lemon).
- Get Fuzzy for April 29, 2014. Satchel the dog hasn't slept for two days, so his master, Rob Wilco, prepares sleep aids such as warm blankets, soft music and warm milk.
- Pooch Café. The page image comes from the June 8, 2014 strip, in which one of the "Human Cures for Insomnia" is a glass of warm milk. The "Dog Cure for Insomnia"? Turn around in a circle and lie down.
- Chancellor Sutler in V for Vendetta enjoys a glass of warm milk every night before bed.
- In Happy Gilmore, Happy's just dropped his grandmother off at a nursing home. She asks the orderly for some warm milk to help her out with the nap he's making her take, but he coldly turns her down.
Orderly: You can trouble me for a warm glass of shut the hell up! Now, you will go to sleep or I will put you to sleep. Check out the name tag. You're in my world now, grandma.
Mrs. Gilmore: Oh, dear.
- Young Frankenstein. While acting as a good hostess, Frau Blucher asks Dr. Frankestein if he would like a glass of brandy before going to sleep. When he declines, she asks him if he'd like some warm milk instead.
- In Pokémon Detective Pikachu, Tim's friend Jack mentions that his mother brought him a glass of warm milk when she mistakenly thought he was having a nightmare (the cries she had heard were coming from a Cubone instead).
- Insomnia: Drinking a glass of warm milk is one of the many solutions offered to Ralph by his friends and neighbors when he starts suffering from insomnia. Since his insomnia has a supernatural cause, it doesn't help at all.
- The Malloreon: At one point, Garion and company are taking shelter at a farm. Ce'Nedra is having trouble sleeping, so heads to the kitchen wondering if the milk is still warm. This turns into an excuse for her to see Silk sneaking into Velvet's bedroom.
- A Song of Ice and Fire: When Arya Stark commits her first killing since she joined the Faceless Men, the master of the guild chastises her for doing it out of her own motives and gives her a glass of warm milk before she goes to sleep. The milk turns out to be spiked with something that makes Arya temporarily blind; fans theoretized that it was punishment for killing without orders, but it turned out it's just part of the training.
- Miss Marple: In Nemesis, Clotilde offers Miss Marple a glass of warm milk when she goes to bed. Miss Marple agrees, on the grounds that it "always gives one a good night". Not that she drinks this particular glass, since she knows it wouldn't be at all good for her.
- In the Adventures in Wonderland episode "The Bunny Flop," the White Rabbit brings the Queen warm milk as she gets ready for bed, and later drinks some himself when his upcoming live TV appearance with the Queen makes him too nervous to sleep.
- In an episode of The Golden Girls, Rose hasn't slept in days (because she's been drinking highly caffeinated tea before bed), and Sofia offers to make her an 'old Sicilian recipe' for sleep that always works. Rose takes a sip and says it's only warm milk as Sofia stands behind her and raises a frying pan to hit her in the head. "Don't worry, you'll feel it in a second."
- Green Acres. Averted in "Horse? What Horse?" where Lisa believes Oliver has lost his mind, because he keeps seeing a polka-dot horse, that quickly disappears when he tries to show it to her. So because of this, Lisa decides to sedate him to sleep by dropping a sleeping pill in a glass of milk. Because she keeps getting two different glasses mixed up, Hilarity Ensues, and she's the one who gets knocked out, while Oliver figures out what she was trying to do, because he doesn't like milk.
- Stargate SG-1: Teal'c, at one point, is experiencing difficulty undergoing kelno'reem (a trance state Jaffa enter instead of sleeping). Carter suggests a glass of warm milk. Teal'c's response, delivered in usual stoic, deadpan tone:
Teal'c: I would prefer not to consume bovine lactose at any temperature.
- Star Trek: The Next Generation:
- Picard's Aunt Adele has a recipe for steamed milk that he shares with Beverly Crusher. She then shares it with Will Riker.
- The page quote is from "Hollow Pursuits", where it's said that Reg Barclay usually orders a glass of warm milk when he's in Ten Forward. Guinan seems to agree with the idea, as she tells Geordi LaForge when he chuckles at it.
- Discussed in the Star Trek: Voyager episode "Unforgettable"; Chakotay asks Neelix for something to help him sleep, upon which Neelix lampshades humans use warm milk. They both find the idea repulsive, however.
- In the Book of Judges, a woman named Jael murdered an enemy general by bringing him into her tent, giving him milk when he asked for water, and driving a tent peg through his temple when he fell asleep.
- Pink Panther: Hokus Pokus Pink:
- While in Siberia, the solution for getting into the village food shed without being bothered by the Angry Guard Dog is heating up the milk pouch Pink finds earlier in the game, and then give it to the dog. He will drink the milk and promptly fall asleep. You can also try to give the dog the milk while it's still cold, but this only results in him throwing the pouch back at Pink.
- And if you try to give the warm milk to Chuki instead, she will lampshade the trope, pointing out how warm milk makes her sleepy. Which she doesn't want since it would make her miss her favorite show.
- Classic Disney Shorts: "How to Sleep" has Goofy trying to sleep by drinking warm milk, but it is too hot for him.
- Cow and Chicken. In the episode, "Stay Awake," Chicken eats a bowl of caffeine-enriched coffee cereal, that includes a side effect of three-night sleep deprivation. Sure enough, after three nights of being hopped up on caffine, and sleep deprivation, Chicken loses his mind and goes berserk throughout the city; Cow tries everything in the book (literally) to help Chicken fall asleep, from knocking him out with bricks, to duct-taping his eyes shut, to rocking him like a baby, to hog-tying to his bed, to counting sheep, until she finally finds the sure-fire cure: warm milk. As Chicken wigs out on the top of a skyscraper, Super Cow comes to the rescue and shoots warm milk into his mouth, filling his stomach (and then some); she then takes him home and puts him to bed, where he finally falls asleep.
- Garfield and Friends: In the U.S. Acres episode "Sleepytime Pig", Orson is unable to go to sleep, so Wade offers him an entire pailful of warm milk as one of many methods to try to help Orson sleep. After Orson drinks the entire pail, he only moos like a cow instead, making this a subversion.
- Ed, Edd n Eddy. Invoked in an episode where Ed starts sleepwalking and eating all the food he can get into his mouth one night. The episode title is "A Glass of Warm Ed".
- The Loud House: In Pasture Bedtime, in order to ditch Liam so they can go to Girl Jordan's pool party, Lincoln and friends convince Liam to drink a glass of fresh goat milk, which they themselves quickly dispose of so only he drinks it. It works and he falls asleep.
- In an episode of Peppa Pig, George catches a cold. Dr. Brown bear recommends he be given a glass of warm milk to help him sleep at night. He takes it, and it helps him feel better the next morning.
- Rocko's Modern Life. In the episode, "Sailing the Seven Zzzs", Mr. Bighead starts sleep walking, which is induced by nightmares of a childhood experience of bombing in a school play due to stage fright. Because he was a pirate in the play, as he sleepwalks, he dreams of being a pirate, and continually pillages Rocko for a treasure map; though Rocko can see that he's sleepwalking, and tries to calm him down, among other ways, by offering a glass of warm milk.
- One episode featured the babies imagining that they were in a noir story a la The Maltese Falcon. Warm milk was used by Lil's Femme Fatale character as the equivalent of a drugged drink for Tommy's detective character.
- In the episode, "Sweet Dreams", Chuckie is trying to fall asleep so he can have exciting dreams like the other babies. Didi comes into Tommy's bedroom with a tray full of warm milk to help the babies fall asleep. The other babies give Chuckie their milk, in hopes that it will help him fall asleep. It doesn't work, instead making Chuckie have to go to the bathroom.
- In one episode of Shirt Tales, Kip Kangaroo can't sleep, so she goes looking for warm milk to drink.
- The Simpsons:
- In "Who Shot Mister Burns?", Chief Wiggum plans to drink some coffee to keep himself awake. However, he can't find any coffee, so he drinks a carton of warm cream instead. This naturally has the opposite effect and he falls asleep.
- In one of the alternate timelines Homer creates in "Treehouse of Horror V", Ned Flanders is supreme ruler of the Earth. One of his methods of maintaining control is reprogramming people by subjecting them to "a glass of warm milk, a little nap, and a total frontal lobotomy."
- SpongeBob SquarePants:
- In the episode "Suds", SpongeBob goes to the kitchen to whip up some warm milk and a seanut butter sandwich to make him sleep again. One bite of the sandwich and he promptly goes to sleep on the table, spilling his milk, and leaving the fridge door open, thus kicking off the plot.
- In the episode "Fear of a Krabby Patty", after SpongeBob experiences hallucinations of giant Krabby Patties, Plankton, dressed as a therapist, hypnotizes him to sleep, and in the dream, a giant Krabby Patty brings SpongeBob a cookie pizza and a glass of chocolate milk to comfort him.
SpongeBob: The king of flavored dairy drinks! [he drinks it quickly]
- In "New Digs," SpongeBob drinks warm snail milk. He falls asleep quickly, then realizes that he is late for work when he wakes up.
- Subverted in "InSPONGEiac." To cure his insomnia, SpongeBob drinks a lot of milk. Being a sponge, it sprays out of his holes and he still cannot sleep.