A prank that has been done lots of times throughout the years, this is when a character places a thumbtack in a chair, and when another character sits down, what results after that is a pained jump due to the sharpness of the tack. In cartoons, this may sometimes result in a Pain-Powered Leap. Also the rare prank that women (usually schoolteachers) tend to be the victims of more than men.
Related to the Whoopee Cushion, but much more painful. May be just as embarrassing. Compare Butt Biter and Rump Roast. Subtrope of Literal Ass-Kicking, as it results in a literal pain in the butt. Do Not Try This at Home - its technically assault, especially if the tack breaks the skin and could leave the victim requiring a tetanus shot if their boosters arent up to date.
- In The Incredibles, it was implied that Dash did this to his teacher at school. The teacher claims that he caught him on camera, but when the tape plays, Dash moves too fast to actually be seen, which allows Dash to get off easy.
- Frame-advance actually does catch Dash mid-placement of tack, for the curious. In fact, it is possible to watch the split-second moment occur in regular speed.
- A variant in the live-action Dennis the Menace film. Instead of placing a tack in a chair, the babysitter's boyfriend places a tack on the doorbell, not knowing that it was Dennis who was ringing the doorbell. Before Dennis can ring the doorbell again, Mr. Wilson shows up, prompting Dennis to come back in through the pet door so Mr. Wilson ends up the victim of the thumbtack prank instead.
- In The Little Rascals short "Readin' and Writin'", one of Brisbane's pranks is to put tacks on all of the other students' chairs. Miss Crabtree has everyone sit down on her count, leading to a chorus of yells.
- This was a common gag on The Three Stooges, though normally it'd be something even more sharp and painful than thumbtacks. One instance where thumbtacks were used came when the Stooges infiltrated the office of a high-ranking Nazi officer, and placed a map with thumbtacks in it on his chair.
- A variant occurs in The Sound of Music. The Von Trapp children place a pinecone in a chair that Maria was going to sit in.
- In the second-to-last The Wheel of Time book, Elayne is about to sit on the throne of Cairhien for the first time, but Birgitte insists on checking it, to her annoyance and embarrassment. This disappears when Birgitte finds a poisoned needle on the seat.
- In Little Town on the Prairie, a schoolboy in Laura's class is the victim of this prank (with a bent pin), causing the Sadist Teacher to have him stand in the corner for making a scene in class. (She was going to hit his palm with her ruler, but couldn't find it in her desk.) Later, when the boy recounts the incident to the school board, he glibly remarks, "I was not punished for sitting on it, but for getting up off it." The board has a hard time stifling their laughter, and has to admit it's Actually Pretty Funny.
- According to Osipko Khripunov's biography from The Newest Plutarch, Ivan the Terrible, when a senior nobleman once complained that he's supposed to sit by the Czar's side, told him to do just that... while putting a needle in the seat. Khripunov has then gained the Czar's favor by asking to sit on that chair despite the needle.
- Once in Hogan's Heroes, Hogan puts Klink's spiked helmet on his chair.
- In the Homestar Runner short The Interview, Strong Bad tells Homestar that he wants to "get down to brass tacks". Homestar seems to think he's talking about actual tacks and replies "Oh, I didn't bring any."
Strong Bad: (to himself) Oh, this is gonna be painful...
Homestar: The tacks? I'll bet. Try not to sit on 'em.
- In the SuperMarioLogan episode, "Substitute Teacher!", Bowser Junior and Joseph dare Cody to put thumbtacks on Jackie Chu's chair to prank the substitute teacher, which Cody reluctantly does. Cue an "Oh, shit!" from Cody when he finds out that Judy is the substitute teacher.
- One episode of Viva la Fegel has Fegelein do this to Hitler, among other antics.
- In The Simpsons when Marge becomes Bart's substitute teacher, he didn't know his mother would be teaching him beforehand and quickly rushes to remove the tack he placed on her chair. He then has to rush back there again when he remembers the other booby trap he put there: a giant swinging log on a chain.
- A memorable Tom and Jerry short involves Tom trying to keep quiet to avoid waking up a sleeping king. One of the methods that Jerry and Nibbles makes this difficult for Tom is by placing a pin under Tom just as he's about to take a seat.
- One episode of Invader Zim had Zim pull the seat tack prank on Dib. Dib believes that Zim's prank is pathetic, even for Zim, until he realizes that the tack contained mutagenic contamination that was slowly turning him into bologna.
- In the Adventures of Sonic the Hedgehog episode, "Super Robotnik", Scratch hangs up a picture in Robotnik's office and one of the nails accidentally falls on Robotnik's chair. Since Robotnik's butt was the only thing that wasn't affected by the Superpower formula Coconuts inadvertently created, it wasn't invulnerable like the rest of his body. Thus, he is in geunine pain when he sits on the nail.
- On the Gerald McBoing-Boing short "How Now, McBoing-Boing", Professor Joyce, and expert on human speech, is brought in to try and cure Gerald, who can only communicate through sound effects. One of the methods he tries is to make him sit on a tack, in the hope that this will cause him to let out an reflexive "Ouch!" Instead, Gerald makes a sound like a car tire blowing out, then gives Prof. Joyce a Death Glare.
- In the 3-2-1 Penguins! episode "Practical Hoax", Baron von Cavitus' first minion places a Tell-a-Liar (a dart-like alien) on Midgel's chair.