He could be working at Burger King, spitting on your onion rings
A subtrope of I Ate WHAT?!, this is when a person decides to get revenge on someone by tampering with their food. This can range from slipping in an ingredient that breaks a cultural taboo (giving shellfish to a kosher-keeping Jew or meat to a committed vegetarian), to disgusting Black Comedy pranks involving overly intimate tampering (bodily fluids), all the way to tricking someone into committing Black Comedy Cannibalism (bonus points for a Familial Cannibalism Surprise).
Unlike the sister trope Tampering with Food and Drink, the added ingredient is not meant to cause physical harm to the victim, but rather to insult and disgust them. (That said, tampering in the form of bodily fluids can carry risks).
Completely unrelated to Best Served Cold, although they can overlap to make the full quote.
- Earl Cain plays this absolutely for drama in Doctor Jezebel's backstory, showing him to have been a sensitive child who loved his pet lamb Snark, and hated to eat meat because he didn't like the thought of animals dying to sustain him. His father told him one night that he could see Snark if he polished off his dinner. Guess what his dinner was.
- In JoJo's Bizarre Adventure: Stardust Crusaders, after Kakyoin defeats Enfant Terrible Mannish Boy, the following morning he finishes him off by slipping a generous spoonful of his diaper's contents in his breakfast.
- In the Pokémon: Advanced Battle episode "Hail to the Chef", Team Rocket enter a restaurant with the food prepared by a Sneasel. After Meowth starts exchanging insults with it, his dish is made painfully spicy.
- Team Rocket fall victim to this again in a Sun and Moon episode. After finding out about the species Ribombee's edible Pollen Puffs, Jessie annoys a wild one by demanding it feed her. James reads through further data of the Pokemon, finding out the puffs also come in poison form to use against enemies. Cue Jessie twitching on the ground as the Ribombee merrily hovers away.
- Rat-Man author Leo Ortolani once made a spoof of the new Star Wars trilogy. The character Dark Mouse, a parody of Darth Maul, was asked by his master (an expy of Emperor Palpatine) about what evil deeds he did that day, and he answered: "Did you think it was beer in that glass I gave you before?". Some time later, the master replied: "Did you think the cake you ate before was a chocolate one?"
- In the Punisher Max, a mafia crime boss and his mooks are meeting with the boss of a rival Chinese gang in his restaurant. The Chinese boss is enjoying a meal and basically telling the mafia guy to go fuck himself. The Chinese boss says he has three strong sons who will carry on the family business and avenge him if he should have an accident. The mafia guy replies that he's a stupid fuck who was too dumb to check out his own place when he showed up for the meeting, that he actually has two strong sons, says that the youngest didn't come home from school, and the reason for that was because the youngest son has been bubbling in that pot on the stove in the back for the past hour. Cue the Chinese boss staring at the plate in front of him in horror.
- In Harry Potter and the Dream Come True Harry puts a spoonful of dirt into his relatives' dinner before serving it to them.
- In Perfectly Abnormal Harry puts a spider in the pancake batter while making his relatives' breakfast.
- Harry Potter and the Lightning Scar:
Kreacher, knowing this was his last opportunity to do battle against the "mongrel half-blood," had made what appeared to be a delicious breakfast—enough that Harry forgot who he was dealing with, and bit into an innocent-looking doughnut. Unfortunately, that doughnut happened to be filled, not with cream or jam, but with mayonnaise. Retching, Harry tried to wash the taste out of his mouth with what looked like pumpkin juice, but which was in fact carefully-diluted muddy rainwater.
- In the Calm Before the Storm side story of The Conversion Bureau: Not Alone, TCB!Big Macintosh reveals he once fed something to Diamond Tiara that gave her food poisoning as retaliation for her calling Applebloom the product of incest.
- In Little Monsters, Brian's monster friend Maurice takes him on a tour of his nightly pranks. For the last house (a bully's house—by request), Maurice switches out the tuna salad in the bully's lunch with cat food and the apple juice with fresh urine. Next day, during lunch, Brian is audience to the hilarity.
- Problem Child 2 has Junior doing this with a pitcher of lemonade that he was asked to refill by two snotty twin girls running a lemonade stand. He tops off the lemonade by peeing in it. Naturally the father of the snotty twin girls buys a glass and drinks it, describing it as tangy.
- In Waiting..., a "beeyotch" makes the mistake of pissing off the waitstaff. Her food is... enhanced, so to speak. And made so that she doesn't even know what she's eating. For the morbidly curious: The cooks put pubic hair, dandruff, and spit on her food. One guy even rubs the garlic bread in his pants and all over his penis and testicles. And for those of you even MORE curious, yes, this is Truth in Television. Always, always, be Nice to the Waiter.
- In The Help a maid who's been unjustly fired gives her ex-employer a "chocolate" pie. When the victim discovers what she'd really been eating, her own mother finds it hilarious.
- Road Trip: a pretty Jerkass cook licks the sugar off some toast and shits on it before giving it back, in revenge for Kyle (the Butt-Monkey of the companions) asking (pretty politely, in an inversion of Unsatisfiable Customer) to remove said sugar. The funnier/more Squicky part is that Kyle never notices this has been done, and actually likes the taste of the toast.
- In re-prints of the novel Fight Club, Palahniuk adds a foreword. In it, he notes that many ex-waiters told him that tampering with food was Truth in Television, including one man who claimed to be a former waiter at a 5-star London restaurant who bragged that Margaret Thatcher had eaten his semen five times.
- This is how Rock in The Stormlight Archive gets sent to the bridge crews. "I may have, uh, enhanced the soup".
Teft: Wait, you put chull dung in Highprince Sadeas's soup?
Rock: Er, yes... Actually I put this thing in his bread too. And used it as a garnish on the pork steak. And made a chutney out of it for the buttered garams. Chull dung, it has many uses, I found.
- In The Help, a servant does this to her employer. Let's just say, it's a chocolate cake, and what she puts into it is brown. She later tells the employer what, exactly, it was. And that's why you should never be mean to the people who cook your food. (Or accept food from people you treated horribly.)
- In I Love Lemonade, Quirky Turkey wants revenge on Little Baa Baa so he puts Billy's pee in some lemonade and serves it to the sheep, claiming it cost money but was free to sheep. However Quirky Turkey added "and turkeys" and ended up drinking it himself. Little Baa avoids it because he believes it looks like pee, but Quirky Turkey had forgotten it had pee in it and seeing as it was free to turkeys, he drank it.
- A Song of Ice and Fire: Lord Manderley serves meat pies to the Frey and Bolton lords who were responsible for his son's death. Roose Bolton is very careful not to eat the pies until Manderley has some himself. The pies are secretly made with slain Frey noblemen.
- The Twits has Mrs. Twit serve her husband worms, calling it pasta.
- Discworld: A certain class of upper-class snobs like to label their alcohol backwards (so that whiskey is read as "yeksihw" and port as "trop") to prevent their servants from stealing sips from the bottles. In response, the butlers top the bottles up with "eniru" after they've had their fill.
- In The Witches, while Luke is infiltrating the hotel kitchen for some food-based revenge of his own, he sees several waitstaff "tenderize" the steak of a rude diner by all spitting on it.
- In the Friends episode "The One With the Racecar Bed", Rachel admits to adding body fluids to the drinks she serves to people who don't tip her sufficiently.
- Subverted in an episode of Trailer Park Boys, when Bubbles falsely tells Barb Lahey that the hot dog she is eating (home-made by Sam Losco) had been 'licked by cats', in order to ruin Sam's date with Barb.
- Seinfeld - George served scrambled eggs secretly laced with lobster to Jerry's girlfriend, revealing it after she ate... many people would love this combination (she did until she knew what it was), but she followed a kosher diet. This was his revenge for her telling his girlfriend about his "shrinkage".
- Game of Thrones:
- When Tyrion Lannister is on trial for murder, he sarcastically confesses to a bunch of misdeeds from his childhood. One of them was jerking off in his older sister's soup.
- Arya serves a meat pie filled with Walder Frey's sons to the man himself, just before slashing his throat and ending him.
- In Classical Mythology, Thyestes, brother of King Atreus of Mycenae, was secretly having an affair with Atreus' wife Aerope. When Atreus discovered the affair, he found two of Thyestes' sons, butchered them, and served them at a feast for Thyestes. After thoroughly enjoying the meal, Atreus informed Thyestes of the secret ingredient, and Thyestes cursed Atreus. That makes this Older Than Feudalism.
- In the WWF in 2001, Commissioner William Regal drank some tea which Chris Jericho had urinated in. He found the taste... interesting.
- The Big Bossman fed Al Snow his (Snow's) pet chihuahua Pepper as "Pepper Steak."
- At one point, Earthquake crushed Jake "the Snake"'s pet boa, then served it as "Quakeburgers" to the commentators. Bobby Heenan was the only one to realize what they were eating before it was too late. He still ate it, being a Heel.
- One Eddie Murphy comedy concert had Murphy talking about how some people make fun of accent or appearance of the owners of Chinese restaurants. In the bit the owner retaliates by making a "special Won-ton soup" for the person insulting him.
- South Park: In "Scott Tenorman Must Die", Cartman is out to get revenge on a teenage boy named Scott Tenorman who tricked Cartman into buying his pubes. Scott tries to humiliate Cartman by tricking him into publicly eating chili containing pubes. But it turns out Cartman's plan was far more sinister, as he tricked Scott into eating chili containing his parents' ground-up corpses.
- Family Guy:
- While Peter uses spy equipment on an restaurant, he hears Mort muttering to himself "Please don't spit in my eggs." and then one cook bragging to another that "I just spit in this guys eggs." There doesn't seem to be any element of payback here, just a cook being an asshole.
- Parodied in "The Kiss Seen Around the World": Neil and Meg are both interns as the same news station, and Neil gets jealous of the attention Meg pays to news anchor Tom Tucker, so he puts "something" in Tucker's coffee. That "something" turns out to be Sweet-n-Low. When Tucker finds out, he angrily throws the cup, as he had ordered Neil to fill it with urine.
- A variation is shown in "the King is Dead." After Peter takes over Lois in directing and producing The King and I she serves him a breakfast composed of random food items. When he asks her what's the deal, Lois says that she did to his breakfast what he did to her production.
- American Dad!: In one episode, Hayley makes the decision to test Roger to see if he cares about anything after she gets tired of his selfishness and jerkassery. She does this test by purchasing his home star and pretending to be its queen. She keeps on annoying Roger with her queenly claims until Roger responds in a way she wanted to all while saying that she won. Roger then decides to get revenge on Hayley for testing him by killing a goat that Hayley donated to an African family and then butchering it and serving it to Hayley and the Smith family for dinner, all while disguising the dish as a lamb dish and then subtle telling Hayley what she was eating by telling her that the dish was "similar to lamb".
- There is an urban legend in the UK about somebody getting sacked by McDonald's for masturbating in a burger.
- One incident that got on a "restaurants from hell" style TV show was where a cook was caught on CCTV urinating into the jar of tomato sauce and then using it to create takeaway pizzas.
- A high school student put his white stuff into a bottle of ranch, which was subsequently used by various people.
- A disgruntled coworker was caught on hidden camera urinating into the office coffee pot.
- Cracked, ever the helpful kind, gives us these horror stories.
- Piss off a bartender and then ask them to make you something good (best done while drunk as shit half an hour before last call) and you may wind up getting a "cement mixer" (a shot of Irish cream followed by a shot of lemon juice; the acidity makes the Irish cream curdle and then stick to the drinker's teeth) or, if you really make them angry, "suicide sludge" or "sewage" (the vile mixture that gets collected in the bar mats poured into a shot glass and sold at a premium price).