Stairs are one of the oldest human inventions, and one that tends to be suited uniquely to a creature with multipedal locomotion using legs of roughly human length. Creatures with differing forms of locomotion sometimes have... trouble with them. Hence this trope.
For some reason, this is often the case with hostile robots, but it's not required to be either hostile or a robot to count as this trope, just a creature or device that logically will often be called upon to deal with stairs, yet has a great deal of trouble navigating them.
Bonus points if the creature attempts to navigate the stairs anyway, resulting in a Staircase Tumble. Extra bonus points if it's actually destroyed in the resulting fall, or disabled so thoroughly that The Hero can dispatch it at his leisure.
A subtrope of Weaksauce Weakness.
- The Lord of the Rings: The Gag Reel for The Fellowship of the Ring reveals this about Christopher Lee's Saruman costume.
- Famously, the ED-209 in RoboCop (1987), ostensibly built for urban law enforcement, was designed without the ability to navigate a simple staircase. Justified in-story, as it was intentionally written as a poorly-conceived design in several ways (spotty AI, major weak points, seriously overarmed), which is why the project was abandoned in favor of the titular character.
- Star Wars:
- Averted in-story, but in full force in Real Life, on the set. In The Empire Strikes Back, C-3PO technically couldn't use the stairs, and the filmmakers "cheated" by having the human characters walk down, the camera would lose 3PO for a second, and he'd rejoin them from behind once they passed the stairs.
- Attack of the Clones shows R2-D2 getting slowed down by Naboo city steps, but he still manages to keep up with the humans.
- In The Force Awakens, BB-8 has difficulty managing a long flight of steps, although he manages to roll down them one at a time with difficulty. In Resistance episode "The Children from Tehar", circumstances force BB to go down a staircase at speed, with the result being that he ends up tumbling out of control and rolling over himself at the bottom.
- Also, see the LEGO Star Wars example in Video Games below.
- Rachel morphs a crocodile but finds out they can't use stairs. Normally she'd just demorph, but there are people watching.
- At one point Jake morphs into a rhino and has some understandable problems using stairs without breaking them.
- Terry Pratchett's Discworld:
- The Golem King in Feet of Clay. Golems are invulnerable unstoppable robotic killing machines created by an alchemical marriage of magic and pottery. There is just one drawback: they are far too heavy for a normal set of stairs to take without collapsing.
- It's "Common Knowledge" in Klatch that you can get a donkey up a minaret, but not down. Of course, in Jingo, Vetinari does just that.
- In Vadim Shefner's story Debtor's shanty, metamorphants are very dangerous creatures which devastated almost all their planet; their flaw was inability of passing by any roughness, but since stairs were not invented on the planet (inhabited by Human Aliens, so it's strange, though justified for them having very different psychology), this was not exploited until terrestrials arrived.
- The anti-heroic Torture Technician Inquisitor Glotka in The First Law, was himself previously the victim of debilitating torture, with the result that while he can use stairs, it causes him agonizing pain, since his torturers smashed bones in his legs and feet and cut off his toes. He jokes to himself that if he could torture any man, it would be the inventor of stairs (and that if he could shake the hands of any man, it would be the inventor of chairs).
- A plot point in Rudy Rucker's book The Hacker and the Ants is the extreme difficulty in designing a robot to handle stairs.
- In Halo: Contact Harvest, Maccabeus the Brute expresses mirth at watching Elites attempt to use ladders, due to their backward-facing knees.
- A Running Gag about the Daleks in Doctor Who.
- Referenced directly onscreen by the Doctor in "Destiny of the Daleks" as the Fourth Doctor taunts a Dalek to try and follow him up the stairs.
- Subverted, however, in "Remembrance of the Daleks". The first episode cliffhanger has the Seventh Doctor fleeing up the stairs and thinking he was safe from the Dalek chasing him, only for it to start levitating up the stairs after him.
- Enforced and subverted in "Dalek", where Rose tells folks the pursuing Dalek won't be able to follow them up the stairs. The Dalek announces "EL-E-VATE!" and begins levitating up them. This was put in after one of the new series writers asked his girlfriend why she thought the Daleks made rather pathetic villains in the original show, and she told him how easy they were to foil.
- A related joke is that real Daleks don't climb stairs, they level the building.
- The B-plot of one episode of Hill Street Blues revolves around Officers Bates, Coffee, Hill and Renko becoming probably the first not-Chicaco-we-swear cops in living memory to arrest a genuine cattle rustler after finding a very large steer in a fourth-floor apartment, and then having to figure out how to get the damn thing back to ground level so they can return it to its rightful owners. The police department eventually have to hire a crane.
- Paranoia supplement Acute Paranoia. The Playing Robots chapter allowed the creation of robot PCs. One of the movement options was "wheels", and the text noted that robots with wheels couldn't go up stairs.
- Classic Traveller Adventure 2 Research Station Gamma. The animal care, janitorial and security robots cannot climb stairs because their movement systems won't allow it. They have to use the station elevator instead.
- In the fandom for Warhammer 40,000, it's commonly joked that the 7 to 10-foot tall Super Soldier Space Marines cannot use stairs because their enormous Powered Armor boots can't physically fit on stairs built for humans. Official art depicting the Space Marines gets around the issue by giving all Imperial buildings ridiculously huge architecture with stairs two meters long per step. Tactical Dreadnought marines get around the issue by just teleporting up or down.
- The robot Claptrap in Borderlands. In the second game, this is pointed out, and the player is forced to use a crane to hoist him. It comes up again in the final mission where this very weakness keeps him from joining you in the final battle against Jack.
- Averted in Borderlands: The Pre-Sequel!, in which Claptrap is playable, the justification being that Handsome Jack installed a special wheel on him that he removed once he destroyed the entire Claptrap line of robots.
- The Star Wars examples under Film above actually get carried over into the LEGO Star Wars games where protocol droid characters like C3PO can't jump or navigate stairs. Many levels have sections that require the player to go through an elaborate puzzle-solving process in order to move the droids across the area that the human characters can easily jump or climb a staircase to access.
- In Pokémon X and Y, this is why you can't make off with the Skiddo at the place where you can ride them. They jump ledges but can't do the stairs just outside the broken fence area.
- In Freefall, Qwerty the robot never learned to use stairs. Dvorak (who rolls on wheels) somehow got up, but Qwerty (who walks on legs) can't use stairs.
- The wheelchair-bound Tavros from Homestuck needs to get to the top of his house, so Vriska builds a system of staircases for him. Then she repeatedly pushes him into the bottom stair and tells him to apologize for being paralyzed, which is also her fault to begin with. Kanaya eventually convinces her to build a rocket car for him, at least.
- Lackadaisy: When the bar is attacked by some angry pig farmers, Viktor, who is outside at the start, tries to get back in through the cellar but, due to having been recently kneecapped, finds he can't handle the stairs. Ivy finds him just sitting on the top step.
- Pixie and Brutus: Downplayed; Pixie sees the stairs are a dangerous part of the house that could lead to injury if you're not careful thanks to her small size. Brutus, of course, is unfazed.
- In one post of What If?, written by the creator of XKCD, the question of the week is: "What if there was a robot apocalypse? How long would humanity last?" According to the writer, current robots not only wouldn't be able to chase us upstairs, but might not even be able to get over the threshold of a door.
- On Pelswick, the school bully picks on Pelswick as the favored target, but knows he can't use physical force on a kid in a wheelchair and opts toward psychological abuse. One of his methods was to jump on top of a staircase so Pelswick couldn't follow.
- Robot Chicken had a multi-part sketch where Johnny 5 is Driven to Suicide when he can't ascend the stairs to the basement he came alive in.
- In The Simpsons episode "Grift of the Magi", Bart injures himself and is forced to use a wheelchair. He finds it difficult to enter the school due to the stairs, and Principal Skinner explains the school can't afford a ramp system. Enter Fat Tony of the Springfield Mafia, who offers to build one with his construction outfit, "Valdezzo Bros. Olive Oil". By the time an inauguration ceremony is held for the needlessly complex ramp system, Bart's suddenly healed enough to have no more use of the wheelchair, rendering the whole effort a waste. Skinner pats a ramp in confidence that at least they're ready for "the new millennium", only for the whole ramp system to collapse. It turns out it was built out of breadsticks, paint, and shellac. The mob has conned the school out of $200,000, resulting in its closure.
- Played for Laughs in X-Men: Evolution when Professor X (who is, famously, paralyzed from the waist down) talks to Jean about overcoming limitations... and then finds himself at the top of a staircase.
Professor X: Though, some obstacles are more irritating than others.
- The Roomba. Justified considering how costly it would be to engineer that ability into them. Some of the more advanced models can at least be programmed to avoid them.
- Wheelchairs. Fortunately, various workarounds exist. Not only are there elevator doohickeys that carry chairs up stairs, but there are wheelchairs designed to go up stairs.
- Racing greyhounds have to be stair-trained after retirement, because being caged means they don't learn as puppies.
- Due to their small size and odd proportions (short legs and long body relative to their size), dachshunds don't handle stairs very well, and being made to navigate them too often can cause permanent damage to their fragile spines.
- Some dogs are also afraid of box steps that provide a view of the open space beyond each step.
- It is commonly said that cows can go up stairs, but they can't go down stairs, due to the design of their knees. This is only partially true; cows can go down stairs, but not very long ones or they lose their balance. Many other ungulates such as sheep and horses hate stairs for the same reason, and thus are reluctant to use them.
- Elderly people who are beginning to lose their mobility are likely to have trouble climbing more than moderate flights of stairs.
- Those with arthritis or other joint issues, if knees or hips are affected, tend to find the extra joint flexing involved in stairs rather painful.
- Generally averted by Boston Dynamics. Whether they have two, four, or six legs, their robots can get up and down a normal flight of stairs, albeit usually not as quickly or easily as a human. Subverted by Sand Flea: while its wheels are too small for it to climb up a step it can launch itself up the entire flight In a Single Bound.