There is a set of stairs that has one step that has something wrong with it. Perhaps it's broken, perhaps it squeaks. For whatever reason, the characters have reason to avoid it. And, most of the time, they do. Until that one time when they are in a tearing hurry and they forget all about it. Their foot comes down on the defective step and Hilarity Ensues.
- In the Tintin album Tintin: The Castafiore Emerald, a broken stair in Marlinspike Hall puts Captain Haddock in a wheelchair after he forgets about it, while the repairman keeps procrastinating. At the end of the story, when he is out of the wheelchair and the stair is freshly repaired, he forgets about it again, steps on the still setting marble, and sends himself flying, undoing the repair in the process.
- In Muppet Treasure Island, Benjamina (Ms. Piggy) ruins her huge entrance by tumbling down the stairs. She blames her pet anteater.
- This happens in Who Framed Roger Rabbit when Eddie takes Droopy's elevator.
- Twice in Don't Breathe a squeaky floorboard in the living room gives away the intruders' location to the Blind Man.
- In Snuff Movie, Leon tells the actors not to wander into the west of wing of the house, as the floors are rotten and unstable. Matt disregards this and starts down the stairs, only to immediately put his foot through one. Leon then says that from now on he intends his words to be taken seriously.
- Harry Potter:
- One of the staircases in Hogwarts has a 'sinking stair' that traps anyone who steps on it. Neville usually forgets about it and gets stuck. It becomes more serious when Harry is trapped by it while wearing the Invisibility Cloak in Goblet of Fire.
- There's a more passive example from Chamber of Secrets, when Ron and his twin brothers come to rescue Harry from the Dursleys. As they sneak downstairs to get Harry's belongings, he warns them that the bottom step creaks.
- In The Chronicles of Amber, Gerard keeps insisting that there is a loose step on the stairs to the Pattern Room. No one else ever seems to notice it. Gerard is The Big Guy, literally as well as figuratively, so it's possible that the stair only squeaks under his greater weight. He gets annoyed enough by it that he leaves a note pinned to it with a dagger that says "This one, damn it!" but even knowing which one it is, nobody can find anything wrong with it.
- The Belgariad: Belgarath's Mage Tower has one loose step, which he's been warning people to step over for thousands of years. Garion finally fixes it and finds a diamond underneath, reminding Belgarath that he'd put it there to see how long it would take to grind down to dust, then promptly forgotten. By then, he's so used to the loose step that he puts the diamond back.
- In A Wrinkle in Time one of the steps on stairs (not stairs on the steps) creaks and Charles Wallace uses that to signal to Meg that he wants a conference.
- In Sword of Truth, the condition of the stairs in the house which Richard moves into with Nicci is bad enough that he launches into a full-scale tirade at his three thuggish, knife-wielding housemates, saying something along the lines of "put a shirt on and fix those stairs or you'll never amount to anything". Two of them listen, and do end up better for it. The third is another story.
- Yours Truly: One of the steps on the stairway in the Lovejoy household squeaks whenever it's stepped on. When Mackenzie steps on it, producing a loud noise, Truly's mom calls to her dad to fix it.
- In Muppet special A Muppet Family Christmas, there's a running gag about an icy patch in front of the door. "Careful of the icy patch!" greets each new visitor - after they've already slipped.
- The British one-off drama Number 27 used this seriously as a kind of Chekhov's Gun. One of the characters was an old lady who constantly complained that her landlord would never repair the broken step on the stairs up to her flat. The landlord himself forgot the broken step, tripped on it and broke his neck.
- This happened to game show host Jim Peck on The Big Showdown. The show had a large staircase at the back, and on his way down, Peck tripped on one of the stairs. They left the camera running as he got up, looked at the audience and said, "Sure, you people would applaud a lynching!"
- But was this due to a defective step or Peck simply losing his footing?
- The broken step in the Dunphy house is a Running Gag in Modern Family.
- A variant in Everybody Loves Raymond. When Ray hurts himself in a particularly athletic bedroom session, he claims he tripped on a broken step to his parents. It backfires when turns out the stairs really were broken and Frank falls THROUGH them when he investigates.
- The loose floorboard in front of Parmenter's office was a Running Gag in F Troop.
- Married... with Children has the third step of the basement stairway being broken to the point of being a fall hazard.
- Murder, She Wrote:
- A squeaky board on the stairs (that the killer does not know about) provides a vital clue in "Shear Madness".
- In "The Witch's Curse", Robert Urich's character is laid up in a wheelchair because his stairs were being refinished and he forgot about it: falling down the stairs and fracturing his leg in multiple places.
- Peter Pan Goes Wrong: When Trevor (as Peter Pan) steps on to the table, he steps on a loose plank which flips up and hits him the face, knocking him out.
- Homestuck plays a variation: Tavros is repeatedly warned about stairs, specifically that his new robot legs are not fit for traversing them as of yet. He's got too much self-confidence to heed the warnings, though, and chooses to try going up and down the things to test them out. Much as you'd expect, his legs fail to handle them properly and he trips down them. Repeatedly.
- Which is is a reference to Sweet Bro and Hella Jeff by the same author.
- It's pretty much law in Homestuck that if there are stairs, someone WILL fall down them.
"And watch out for the third step. It's -" *crunch* "- busted."
- This often occurs in classic animated shorts, especially the ones made by Warner Bros., and is usually followed by: "Watch that first step, it's a lulu", or some other variant. Although often, this same phrase was accompanied with a gag where a character would inadvertently walk off the edge of a cliff.
Sylvester: "Watch your step on this bridge. Some of these boards are looooo..." *SPLASH*
- Happens almost word-for-word in Goldimouse and the Three Cats when Sylvester takes his family for a walk:
- Happens in Mickey's Christmas Carol, as Marley's ghost bids farewell to Scrooge and walks through his bedroom wall.
Scrooge: Marley, watch out for that first—!
- Rugrats: As Lou gives Stu, Didi, and Drew a tour of Flushing Waters in "Grandpa Moves Out", he reminds them to watch out for the loose floorboards.