A computer hobbyist/genius builds a computer and/or programs their own operating system, throwing in twists and bizarre logic as they go. They may have a specialized purpose, or only be tinkering. The result is inevitably an ugly mess loaded down with buttons but may prove surprisingly powerful.
Contrast The Alleged Computer.
- Monsters vs. Aliens: Dr. Cockroach is said to have built a computer out of a pizza box, two cans of hairspray, and a paper clip.
- Cyrus Condy's laptop from New Night, which he built in order to communicate with aliens, based on inspiration from nightmares they were beaming into his head at night. The screen is a mishmash of ugly windows, and the language he created for it includes whatever random symbols he could think up to represent the alien concepts he was working with. Bizarrely, when paired with the right hardware, it really can communicate to a galactic network and order services.
- Futuristic Violence And Fancy Suits by David Wong features a super-weapon programmed by mad scientists, in code that is unreadable to other programmers and uses languages that 'don't look human'. Once the last of the scientists is killed, the drivers and software become impenetrable.
- Discworld: Unseen Academy has Hex the thinking engine, which is powered by ants moving through tunnels rather than electrons (hence the slogan "Anthill Inside"). It slowly develops an intellect over the course of the series, asking for and getting more and more parts installed (a ram's skull, a live mouse, a Fluffy Teddy Bear...).
- Richie's computer in the 1980s nerd dramedy Whiz Kids was a cobbled-together, room-filling custom computer—that talked!
- In the The Fairly Oddparents episode "Information Stupor Highway", Mr. Turner builds a new computer using a basket with a light bulb in it for a hard drive, an 80's television for a monitor, a typewriter for a keyboard, and Eddie the Gerbil on a wheel as the power supply. Surprisingly, this makes a fully functional computer.
- The blue aardvark from DePatie-Freleng's The Ant and the Aardvark assembles a computer to advise him how to catch the ant. None of the machine's methods succeed, leading the aardvark to declare, "And for a computer, you stink!" Subverted when the device responds, "Who said I was a computer? I'm an automatic pop-up toaster! And I'll prove it!" The aardvark gets deluged with fresh toast.
- The 1956 Merrie Melodies cartoon "To Hare Is Human" features Wile E Coyote building his own computer to devise ways to capture Bugs Bunny. None of the machine's methods succeed, and the last one results in a crushing defeat. The Reveal is that Bugs Bunny himself was inside the device, and he quips, "The real beauty of this machine is that it has only one moving part."
- TempleOS, a public-domain OS meant to facilitate communication with God. A single programmer, Terry Davis, an American man suffering from schizophrenia, had been developing it since 1993, operating under the belief that God had instructed him to create the OS, and that it was meant be the fabled Third Holy Temple, until his death in 2018 and had written almost every line of code including a compiler, a custom implementation of the C programming language known as HolyC, as well as the entire TempleOS operating system itself. And by his own description, he did most of it on a "a souped-up Commodore 64". The result is almost impossible for a newcomer to use, with an interface full of seemingly random text, garish colors, and inexplicable icons. One programming engineer compared the project to a skyscraper build by one person.