This would be an event or activity that is presented to one or all of the protagonists as being extremely enjoyable. This event or activity never has any redeeming social value; it's just for fun. It's usually presented as being completely innocuous and not at all objectionable — except, of course, in those cases where the basic selling point of the "fun" thing is that it's something the "unhip, uncool" people of the world would never allow one to do. After perhaps some initial reluctance, the protagonists decide to give it a shot. Bonus points are awarded if some "nerdy" character suggests that it's not a good idea, and everyone either ignores or laughs at this person.
When the protagonists finally get involved in the alleged fun, it turns out to be either entertaining beyond their wildest dreams or... well, rather boring. In any case, it certainly doesn't seem to be harmful. But that all changes as the story progresses. Maybe the idea of "fun" being offered up goes way over the line, ultimately breaching the frontiers of good taste or sanity. Maybe the entertainment is actually being used as a cover for some nefarious or destructive purpose. Or maybe the event or activity involves a level of near-suicidal danger that no one could have ever seen coming.
The Trope Namer, of course, is the amusement park in Pinocchio that causes boys to turn into donkeys. (For a time at Walt Disney World, there was a nighttime entertainment district cheekily named after this place and aimed at adults and local clubgoers, though most of the clubs were family-appropriate.)
Often overlaps with The Game Plays You, A Fête Worse Than Death, and/or Crapsaccharine World, and in extreme cases Maximum Fun Chamber. Broader than Amusement Park of Doom, because it can involve just about anything that is ostensibly entertaining. See also Do Not Do This Cool Thing. A subtrope of Too Good to Be True.
- The 1997 thriller The Game. For his birthday, Nicholas Van Orton (Michael Douglas) gets a unique gift from his brother Conrad (Sean Penn). It's a sign-up sheet for Consumer Recreation Services (CRS), which offers customers the opportunity to play an interactive "game." Unfortunately for Nicholas, the only "playing" that ensues is when a conspiracy of complete strangers spend the whole movie mercilessly playing with his head.
- In the 2001 low-budget film Zebra Lounge, a happily married couple become bored with their relationship and decide to meet up with a pair of "swingers" in the city for a night of choreographed adultery. It is all perfectly innocuous (if naughty) fun....until the swingers start stalking them.
- In Teenage Mutant Ninja Turtles (1990), The Shredder has created a "pleasure island" to lure misguided teens into his Foot Clan. His warehouse is located on the ficticious Lairdman Island and features rap music, pinball/video games, basketball, dancing, billiards, skateboarding, gambling, graffitiing, and tobacco use. Newcomers to the warehouse are told "Anything you guys want... We got. Anything you wanna' do... Do it." The naive protagonist in this instance is Danny Pennington (Michael Turney).
- In Hostel the three protagonists have the chance to spend their holidays in the titular hostel in Eastern Slovakia where they can get any girl they want. As soon as they get there, they start having the time of their lives...until they find out that the hostel is owned by a sadistic crime organization that kidnaps tourists and offers them to rich paying customers - who pay to rape and/or torture them in the most gruesome ways.
- In From Dusk Till Dawn the strip bar Titty Twister is actually owned by some vampires who used it to lure trucker and biker in order to eat 'em.
- Bordello of Blood centers around a brothel that is run by vampires to lure in men.
- In Dead End Drive-In, the titular prison camp for unwanted youths lures them in by pretending to be a normal drive-in cinema, and keeps them quiescent with B-movies, junk food, and unofficially sanctioned drug use.
- The Hangover portrays Las Vegas this way, a place where the protagonists go for a bachelor party and nearly ruin their lives in the process. It's subverted for Stu, however, for whom the experience helps him grow a backbone to stand up to his controlling girlfriend Melissa. The sequel repeats the experience with Bangkok.
- The Land of Toys from The Adventures of Pinocchio. A big place for fun and lack responsibilities, but you will be transformed into a jackass. Well, it's the base of the Trope Namer.
- Some Goosebumps books, like Let's Get Invisible and The Horror At Camp Jellyjam, use this trope.
- At the Holiday House in The Thief of Always there are four seasons a day, every night is Christmas, and the House grants any wish, all made possible by a man called Mr. Hood. Eventually though, Harvey's curiosity and growing suspicions about the House lead him to discover some unpleasant truths...
- Animorphs has The Sharing, a Scouts-esque club for community service that is actually a front to recruit hosts for the Yeerk invasion.
- The chocolate factory in Charlie and the Chocolate Factory is arguably a positive version of this trope, in that the kids who get punished in this magical wonderland of a death trap are assholes who deserve it anyway. Mind you, this doesn't always make it less disturbing.
- Edward Gorey's titular The Evil Garden seems fine, but then people start dying.
- The Isle o' Smiles in Dragon Quest VI, reached by mobile island, containing a bar that ferries those who board it from Aridea. It is, of course, a trap. The staff are actually demons, leading to Jamirus, second of the Archfiend's lieutenants. You end up using it as the dream world's water transport, at which point it doubles as an inn.
- One RollerCoaster Tycoon player decided to create an attraction like this in his park. The result: Mr. Bones' Wild Ride.
- Several South Park episodes use this.
- "Chinpokomon" is about a Phonýmon franchise that turns out to be an Imperial Japanese indoctrination tool.
- "South Park is Gay" reveals that the metrosexual subculture was started by evil crab people to turn all men into effeminate sissies and make taking over the world easier.
- "Die, Hippie, Die." A large contingent of hippies arrives in town from Colorado's big cities for a massive 1960s-style music festival; they claim that the purpose of the festival is to stick it to all the corporate bigwigs and other "little Eichmanns" who supposedly run America. Stan, Kyle, and Kenny naively join in the "fun" at first, donning their best "student protester" outfits and learning to play the guitar. But as the festival drags on they start to become bored, and they realize the message of social activism preached by the college kids is, well, pretty much b.s. And on top of it all, all the marijuana smoke is starting to make them sick. They try to leave, but the crowds have become much too thick... until Cartman manages to disperse the crowd with the aid of a: the Hippie Digger and B: a disc full of Slayer tracks (as he said, "hippies can't stand death metal").
- "You Have 0 Friends" portrays Facebook this way when Stan gets sucked into a TRON-esque digital world and has to fight the embodiment of his own Facebook profile.
- The Trope Namer location in Pinocchio features such pleasures as drinking, smoking, property destruction, and playing pool. Indulging in these activities long enough cause the boys to turn into donkeys.
- The Adventure Time episode "Dungeon Train" features a constantly-moving ring-shaped train that tempts adventurers into boarding it. They are lured into constantly fighting monster after monster in the endless succession of carriages for an endless supply of loot trinkets, until they become a "boss" monster and eventually get killed by one of their successors.
- The Futurama episode "Crimes of the Hot" when all the robots in the world were the source of greenhouse gases, Nixon arranges a party at Galapagos Islands inviting all the robots. Despite the obviousness being a trap, Bender goes. The trap being is to destroy all robots with a Kill Sat.
- Drug use and other addictive behaviors. Including this very wiki.
- Unexpected pregnancy and sexually transmitted infections can turn sex into this.
- Pleasure Island is often used as a derogatory term to refer to island destinations that are overrun with tourists, especially if, like the Trope Namer, they bring with them drugs, sex, and other debauchery industries that have a negative impact on local communities. One of the most infamous Pleasure Islands was Cuba in The '50s during the rule of Fulgencio Batista, and one of the major motivations for the Cuban Revolution was to overthrow the American corporations, tourists, and gangsters treating the island as their playground.
- Las Vegas. It was heavily built up by The Mafia, especially after they got thrown out of the aforementioned Cuba, its cornerstone industry remains to this day gambling (an addictive behavior), and the city is renowned for debauchery. The city's unofficial slogan, "what happens in Vegas stays in Vegas", evokes an image of unlimited freedom and pleasure in the closest thing that exists to a legally-sanctioned Vice City full of things that are legal nowhere else but there, but it also has a dark side, indicating that it's also a place where people do things that they go on to regret and refuse to talk about when they get home. The Hangover is built around this stereotype.