Simply put, this is any situation where a character has to force a smile or a please/thank you despite not really wanting to do so.
A few examples:
1) Character A will demand something from Character B. Character B refuses to oblige their request until Character A says "please". Character A begrudgingly does so, and only then does Character B perform the requested action. This is commonly seen between parent and child, though it can occur between adults (typically for comic effect).
2) Character A will want something from Character B. Character B refuses to give it to Character A until they give them a little smile to show their appreciation. Typically, Character A will put on a very forced smile.
It's most common in sitcoms, but can appear in dramatic works occasionally, such as if a villain is trying to smugly exert their power over the hero.
- Everybody Loves Raymond: In "Hackidu", Ray is impatient to get out of Russell's shop with the Scramisaur card, but before Russell will let him have it, he demands, "Let's have a little smile." Ray struggles to force a smile, and after Russell says, "That's what it's all about, man", he says he owes him well over $200 for the purchase.
- In "The Christmas Picture", Ray tells Robert to get over into the picture.
Ray: Get over there.
Robert: "Get over there..."
Robert: There ya go, Raymond. You'll find a little courtesy goes a long way.
- The Simpsons: A variant occurs in "Black Widower" when Sideshow Bob is chewing out a hotel bellboy:
Sideshow Bob: I WANTED A ROOM WITH A FIREPLACE, YOU BLASTED MONKEY! (realizes Selma is capturing him on camera) Oh Selma dear... I was just chatting with my good friend... (looks at his name tag) Dennis! Now, smile for the camera, there's a good lad! (Dennis struggles to produce a nervous smile)
- Teen Titans: Robin is being forced to take a supervillain's daughter to her prom.
Kitty: And would it kill you to smile?
- Subverted in The Dresden Files, where Harry is trying to negotiate a deal with local crime boss Johnny Marcone.
Marcone: Say "please".
Marcone: Say "pretty please".
Harry: Pretty please...
Marcone: Say "pretty please with a cherry on top".
- Farscape however plays it straight, when John Crichton finally agrees to give Scorpius the wormhole weapon he's been obsessed over for years. John goes all the way to "pretty please with a cherry on top" with Scorpius repeating his words without hesitation.
- Subverted in one episode of Rugrats, where Angelica has taken a ball from Tommy, who wants it back.
Angelica: Ask me nice.
Tommy: Give me my ball!
Angelica: Say "Pretty please with sugar on top."
Tommy: Give me my ball!
- Star Trek: Voyager. In "Message in a Bottle" B'Elanna gives Seven of Nine a lengthy tirade on how rude she is, not even delivering common courtesies like "Thank you". Later Seven zaps unconscious an annoying alien who's giving them trouble.
Seven: It was a mild shock. He will recover. He was not responding to diplomacy.
Seven: Thank you.