A D.I.Y. Disaster is when a device's faulty nature is shown by the fact that when a button is pushed or a lever is pulled that is supposed to do one thing, it does something else that a different button or lever is supposed to do, such as a car's window button activates the windshield wipers. It's frequently used after someone has tried to repair or modify the device in question to show their mechanical ineptitude. In spite of the name, this doesn't need to be the result of a botched do-it-yourself job; the device could be wired that way on purpose, for example. There's also a variation where the electricity and plumbing (and sometimes the gas) get mixed up, so you get water coming out of the lightbulbs or some similar mix-up. Doesn't make the slightest bit of sense, but Rule of Funny applies.
Not to be confused with What Does This Button Do?, where a person's inexperience with the device in question, rather than the device's faulty nature, causes the unexpected result. If a person doesn't know what a button does and presses it anyways, something unexpected happens, and hilarity ensues, it's What Does This Button Do?. If the button is supposed to do one thing, but when pressed, does another, it's a D.I.Y. Disaster.
Though a D.I.Y. Disaster can be an Epic Fail, an Epic Fail that results from a do-it-yourself project is not necessarily a DIY disaster. If a person presses a button and something completely unexpected happens that shouldn't have happened at all, it's an Epic Fail. If a person presses a button and something happens that's supposed to happen when they push a different button, it's D.I.Y. Disaster.
Similar to Wiper Start, although a D.I.Y. Disaster is the result of the design of the car, not the incompetence of its operator. One of the worst results that can come about from Doom It Yourself or a Do-It-Yourself Plumbing Project. Almost always Played for Laughs.
- An insurance commercial has a guy inside his house flipping a light switch up and down and looking around trying to figure out which lights it controls. It then cuts to an exterior shot of the house showing that the neighbor's garage door is going up and down in time with the lightswitch, crushing their car under it.
- An ad for an energy bar (or something) shows a contractor fruitlessly trying to turn on a natural gas fireplace by flipping the switch, while his partner yells for him. Turns out that every time he flipped the switch, fire shot out of the toilet, trapping his partner in the bathroom.
- In one Donald Duck comic, the nephews cause the Duckburg supercomputer to go haywire, resulting in this kind of weirdness happening all over town: radio songs come from toilets, TV sets flood, etcetera.
- In Eppo, an old Dutch comic, the eponymous character once switched the gas and water pipes in a Do-It-Yourself Plumbing Project. Cue water streaming out of the heating part of his boiler and the shower turning into an impromptu flamethrower.
- Gaston Lagaffe meddled with the office building's plumbing once, causing water to spray from Mr. Boulier's heater. On other occasions he turned a fridge into a pressure cooker, made a motorcycle ride in reverse and switched around all the keys on a typewriter.
- An earlier attempt to inspect the fire extinguishers in the building resulted in him setting them on fire. All of them. The whole event is explained after the fact by Fantasio, so we don't see what happened.
- Big Fat Liar: The protagonists purposely wire Marty Wolf's car to do this, with the brake making the car horn go off, and a lot of other stuff.
- The Empire Strikes Back: Han and Chewie's attempts to repair the Millennium Falcon provide some comedy in an otherwise very serious movie. The Falcon might be the fastest space freighter in the galaxy, but Han and Chewie (probably mostly Han) achieved this at the cost of hot-rodding the engines so hard that they're constantly on the edge of a catastrophic failure every time they're run up to full power. This includes a scene where Han tells Chewie to power up a system that Han just repaired, and it proceeds to blow up in Han's face, causing him to frantically shout for Chewie to turn it off.
- The Man with One Red Shoe: Agents bugging Tom Hanks' hotel room have to make a hasty exit. Jim Belushi, having to use his bathroom, discovers that flushing the toilet causes faucet to run, etc.
- The Three Stooges: In the short A Plumbing We Will Go, Moe, Larry and Curley posed as plumbers to escape arrest, and are accidentally hired to fix a minor leak in a mansion. By the time they're done, they've left water coming out of everything but the faucets. And we do mean everything, including the light fixtures, and even an early model DuMont television set.
- In Discworld, Bloody Stupid Johnson's attempt at a housing complex turned into a four-dimensions nightmare, and his mail-sorting machine was some sort of black-hole-matter-shredder thing, mainly because he thought it would be less trouble to try and include a wheel with pi of exactly three... and succeeded.
- Newspaper columnist D. L. Stewart recounts, via his book Fathers Are People Too, an attempt by him and his neighbor to install a light fixture in the basement. They make two critical mistakes in the process: first, they forget to turn off the power before removing the old fixture (leading to the neighbor standing in the middle of the room with a melted screwdriver in his hand), then they do the wiring wrong, causing the upstairs lights to turn off when the downstairs lights turn on. Fortunately, both of these problems are successfully fixed in the end.
- On The Brady Bunch, Greg bought a used car and tried to fix it up, part of the result of which was faulty wiring. The horn made the windshield wipers work, for example.
- Family Matters centered an episode around a do-it-yourself home bathroom repair idea. Naturally, the toilet flusher ends up turning on the shower, the sink ends up turning on the bathtub, the bathtub ends up turning on the sink, etc.
- Everything Carl does kind of turns up this way, doesn't it? It becomes something of a Running Gag.
- Friends had an episode subplot that revolved entirely around Monica's frantic search to find out what a power switch did, digging up walls and the floor in the process. In The Stinger, it turned out that it turned on and off the television set in the other apartment, and it turning on and off corresponded perfectly to Phoebe's blinking, leading her to claim she had 'special powers'.
- George & Mildred: When Jerry installs a shower for the Ropers, he somehow manages to hook their shower up to the plumbing of their next door neighbours.
- Subverted in an episode of The George Lopez Show. George tries to demonstrate that his kitchen sink repair worked, and the entire kitchen begins rumbling. It's quickly revealed that the rumble is being caused by an actual earthquake.
- In Get Smart, Maxwell Smart would have cars with crossed wiring, so a button meant to operate one thing instead operated another. His apartment was also crosswired that way. Oddly, this is not necessarily another instance of his incompetence; he at least knew how the crosswiring worked. As it made for an effective security measure, he may have even done so on purpose. At the very least, he could exploit it.
- This appears to be a continuation of the Shoe Phone gag. In one episode where Max and 99 are undercover as news agents, they are given (a) a camera disguised as a tape recorder and (b) a tape recorder disguised as a camera. When the Q-type is asked why he didn't just give them a camera and a tape recorder, he replies "my mind doesn't work that way". So Max's apartment and car continues in this spycraft obsession with disguising one object as another object.
- In The Golden Girls, when Dorothy and Rose try to fix their bathroom themselves, their first attempt leads to them redoing the plumbing such that flushing the toilet makes the sink run, the spigots on the sink control the shower, etc.
- There was a Hannah Montana episode that centered around this. The kitchen sink led to one of the upstairs bathrooms, resulting in what Billy Ray Cyrus called a "Mushu-y Shampoo-y", and other complications when Jackson had tackled the aforementioned sink. In the end, though, it turns out that his dinking around saved their house.
- Home Improvement. Although Timís tinkering and tweaking usually ends in things shorting out, crashing, or exploding, he has his moments of this trope, too. For example, during one of his hot rod builds, he tells Mark to cover his ears when he tests out the freshly-installed horn. However, the horn button actually turns on the high-beam headlights, blinding Mark instead of deafening him.
- A very sad example on an episode of Homicide Hunter. Lt. Joe Kenda arrives at a house to find all five family members dead. Initially perplexed, as there are no signs of violence, he soon notices their cherry-red complexion—the classic sign of carbon monoxide poisoning. It turns out that rather than hire an expert, the family's landlord decided to replace their heater himself, but obviously had no idea what he was doing.
- On Perfect Strangers, Jennifer and Mary Ann go away for a trip. Before leaving, Jennifer asks Larry to call the plumber for her and let him into their apartment to carry out some repairs. Larry of course decides that what Jennifer is really saying is that she wants him to do the repairs and doesn't bother to call the guy. Sure enough, he has no idea what he's doing and ends up flooding the girls' apartment.
Larry: Instructions? I don't need instructions. My father once rewired our entire house without instructions.Balki: Was that the house that burned to the ground?
- On Pixelface, Romford's attempt to 'upgrade' the kettle somehow results in the toaster launching Projectile Toast at Alexia.
- Most of the humor on The Red Green Show is derived from this sort of thing.
- Occurred on one episode of Scrapheap Challenge when a car's wiring loom had been cut. After the first attempt to reconnect the severed wires, the wipers ran whenever the ignition was on.
- One episode of Sports Night features Jeremy's decision to personally Y2K-proof the studio. After getting everybody's cooperation in staging a mockup show to demonstrate his work, he apparently manages to blow out everything electronic in the studio, shortly before the live airing of the real show. This leads to the rest of the cast scrambling to do the show from a different and disliked studio while Jeremy suffers a Heroic BSoD. At the end of the show he was finally informed that, last night, after he'd left, the electricians had done some work behind a console without relabeling the buttons... so that instead of starting the test, he'd hit the main power switch.
- On an episode of That's So Raven, a very prominent business man is to visit Victor's restaurant. Victor creates a Foreman grill-type device that both "grills and chills." He demonstrated his creation by having it grill a steak and chill some jumbo shrimp. However, he crossed a few wires and instead, the grill flash freezes the steak, and the chiller turns the shrimp into charred lump with tails.
- Parodied in the Saturday Night Live skit "In Over Your Head", when it turns out that the host is just as inept as the people he's advising.
- In the Batman: The Brave and the Bold episode "Darkseid Descending!", Skeets's attempts to fix the air-conditioning on the satellite results in it spouting out flames.
- Inspector Gadget does this with voice activation. "Go Go Gadget balloon! No, not pontoon, balloon!"
- In one episode of King of the Hill, Bill's kitchen is one of these. Flipping the light switch, for example, causes the microwave to start. This inspires Hank to do something similar with his own kitchen to discourage a pair of Hipsters from buying his house, which Peggy had accidentally sold.
- The Simpsons: Homer Simpson is a frequent offender. When he is showing his half brother around the house, he flicks a switch that he doesn't know the function of, which turns on the Christmas lights on the roof (which have been there since 1985).
- Wunschpunsch: In "Appliance Alliance", Bubonic and Tyrannia cast a spell to make appliances revolt against their owners. When Tyrannia decided to bake a cake to celebrate, she realized that she forgot to protect her own appliances against the spell. One of the consequences was her refrigerator spouting flames.
- In a rather somber example, a hospital, due to a construction mistake, ended up having oxygen in the nitrous oxide line and nitrous oxide in the oxygen line. Death and lawsuits ensued.
- In the book We Almost Lost Detroit, the many hilarious hijinks involving the Fermi Nuclear Power Plant are detailed. One of which includes the fact that right before it opened, someone had noticed that the pipes to the drinking fountain apparently originated from the area that was responsible for storing the coolant water.
- Averted by the Manhattan Project where people working on the atomic bombs claim to have had dreams of wires being crossed prior to completion only to show up the next day and find out the wires really were crossed and fixing them. The first test of the atomic bomb, called Trinity, worked flawlessly.
- A reputed prank to create the same effect in a school lab is to connect the water and gas taps with a hose, and briefly turn both on. Then when the next class want to use the bunsen burners, water will come out of them.