A sub-trope of the Bar Brawl. Sometimes, you don't have to go to the Bad Guy Bar in order to have a beat down. Sometimes, all it takes is a trip to the local Greasy Spoon. One or more characters are trying to have a nice meal when an inexplicably aggressive diner patron decides to pick a fight. The inexplicably aggressive patron might even have one or more inexplicably aggressive friends backing him up. This will result in an altercation of some sort, despite the character's best efforts to avoid a fight.
This scene might play out in more family friendly movies where a bar could be seen as inappropriate. Maybe the scene involves teenagers, so a bar is certainly out of the question, but the writers still want to invoke the same idea as a bar brawl. It's also possible that the writers simply wanted to move the action to a different locale in order to have a nice breath of fresh air. Unlike the Bar Brawl where the hero is usually guaranteed a winner, this scene might have a more unfortunate result. Sometimes, the scene is meant to show how meek the hero is before having his or her final moment of glory. They may even end up Paying For The Action Scene.
Occasionally the Porting Disaster of the Bar Brawl, when, after a night of drinking, the consumption of other substances and tension-building, the combatants-to-be have retired to a diner or restaurant for a meal.
See also Food Fight. Compare Wok Fu.
The Invisibles. A local cowboy doesn't like the fact that Lord Fanny is a transsexual and tries to pick a fight. Doesn't go well when the heroes take down entire military bases on their off days.
The graphic novel Mesmo Delivery begins with a fight between the main characters in a truck stop.
A backup feature in Savage Dragon shows Zeek eating at a diner that happens to be owned by a superhero couple: Rock and Widow. Zeek does not realize he has to pay for a meal so a fight erupts between him and Rock, which resembles the old 1960's fights between The Incredible Hulk and The Thing. Eventually, the matter is solved by Rock employing Zeek.
Every Astérix book in which the heroes journey outside the village will feature at least one punch-up in a restaurant.
In Superman II, Superman loses his powers and is reduced to mild mannered Clark Kent. He visits a diner, only to be harassed by a truck driver and roughed up. Later in the movie when he regains his powers, he goes back to the same diner and throws the truck driver down the length of the counter. He leaves, claiming that he's been working out.
In the first Back to the Future movie, Biff and his gang bully George McFly while in a diner and then turn their attention to Marty once he tries to stand up to them on behalf of his dad. Later, the characters go back to the same diner to beat up George only to have Marty trip them and sucker-punch Biff. This leads to the famous chase sequence outside. In the sequel, it's Biff's grandson who bullies Marty's son, leading to a similar sequence of events.
In U-Turn, another movie directed by Oliver Stone, Sean Penn's character gets beaten up in a diner by a jealous boyfriend who is pissed that his girlfriend has a crush on him. He actually gets beaten up a lot in this movie.
Averted in Dumb and Dumber when Harold throws a salt shaker and accidentally hits a large redneck named Sea Bass in the head. Sea Bass marches over to the two men and is ready to kick their collective ass until they apologize and offer to pay for his meal. They end up sticking him with the bill instead and flee the diner.
In Howard the Duck, Howard has to fight for his life inside of a diner in order to avoid being cooked and served to customers. The Big Bad enters the diner during the same scene and begins attacking.
Played for laughs (note the obvious stunt double) in I'm Gonna Git You Sucka when Mr. Big's goons arrive at a local diner to beat up Jack Spade. Luckily Jack's mother is there to protect him, much to Jack's chagrin. Watch it here, 6:45-7:45. Includes a Bar Slide.
Love And Death On Long Island has an in-universe example. John Hurt watches a Movie Within a Movie called Hot Pants College II which apparently starts with a scene of holligans beating up Jason Presly at a 50's style diner.
The James Dean movie Giant. Seen here. Rock Hudson is the one delivering the beating, however.
A History of Violence has a very violent, yet important instance of this trope. After the main character kills two robbers in his diner, it begins a cycle of violence and unearths his shady past.
Secondhand Lions has a memorable brawl, with Hub giving the teen delinquents who are hassling him fighting lessons, then working off some angst on them, then bringing them home to provide first aid and a lecture called "what every boy needs to know about being a man".
The film Legion involves angels attacking a lone diner and its patrons in order to bring about the Apocalypse. One of the first scenes shows an angel in the guise of an elderly woman brutally attacking the main characters until she is shot dead.
In Streets Of Fire, we're introduced to our hero Tom Cody when he arrives at a diner and finds some 50s-style bikers getting out of hand. He beats them all up and makes a big mess of the joint. It turns out that the hostess is his sister and a little annoyed that he trashed her business while protecting her honor.
An early storyline of ER had a doctor and her husband being diagnosed with HIV. The husband had not known about this and accidentally infected a co-worker during a work-related accident. The co-worker saw the doctor and her husband in a diner in one episode and began to harass them until the husband stepped in and fought him. It was one of the more dramatic examples of this trope.
Red Dwarf had a reversed diner brawl in episode Backwards. It started with a patron uncracking Listers ribs, proceeded with Lister being thrown across a table, and finally Lister putting a tooth back into someone's mouth before the bar returns to normal activity.
An episode of Community depicted the cast dressing up as Pulp Fiction characters in a diner for Abed's birthday. When Troy damages Abed's gift by accident, he and Chang get into a fight in the diner, resulting in them hitting the jukebox.
In the first episode of The Aquabats Super Show!, "ManAnt!", the extremely famished band attempts to order at a deserted burger joint when ManAnt's henchmen show up to attack.
In Harry Potter And The Deathly Hallows, the main characters run into a diner to escape the Death Eaters, but two show up because they are able to track anyone who speaks Voldemort's name.
A Nightmare on Elm Street: Perchance To Dream has a Fast Food Restaurant Brawl, caused by everyone being rendered edgy, paranoid and violent due to Jacob Johnson stopping everyone in Springwood from dreaming for at least a month (to protect them from Freddy). Later on in the police station patrons are still fighting, with several cops now involved.
Search for "Dennys Brawl" and at least three different viral videos will pop up depicting nasty fights witnessed in the diner-chain. They must be putting something in the Moon Over My Hammy
Denny's, both in Japan and in cities in the US where they may be, has become popular among the Yakuza for some reason. There was at least one fatal shooting at a Denny's in Japan that happened when two enemy yakuza members met.
This tends to happen at 24 hour diners or open late diners in general. Often, 24 hour diners or late-open diners are in areas with a lot of nightlife. The Diner Brawl in these cases is often just a Porting Disaster of the Bar Brawl.
The famous Mel's Diner in West Hollywood was trashed in a particularly nasty late-night food fight that turned into a violent brawl. And of course, it's up on YouTube.
Mel's Diner on the Sunset Strip is somewhat known for these, for the above reason - its nightlife proximity.