There's a pretty good video on the history of the Game Boy, if you don't have 30 minutes (some of the tech stuff might be a bit long for some) here are some interesting things summarized about it. It actually provides a lot of fascinating detail into Nintendo being an almost high school like culture where the different cliques (R&D development teams) sorta hated each other.
- Gunpei Yokoi has been hailed as the father of the Game Boy ... but this is only kinda half true. The truth is Yokoi was upset about the success of the Famicom and being upstaged by R&D2 (makers of the Famicom who were already working on the Super Famicom/SNES by the time the Game Boy was in development). Yokoi actually hated the idea of a "portable Famicom". He wanted something more simple like an upgraded Game And Watch with very simple basic games that were more toy like and a device that would be thrown away after a couple of years. There was also supposed to be some kind of gimmick like attaching a piece of paper or film to the screen ... I didn't really get this part, but it was supposed to be more like disposable toy with more basic G&W style games.
- Yokoi was generally bitter that Nintendo was becoming more about game consoles than toys. His expertise wasn't in tech, but more design. Satoru Okada might more accurately be the actual "father" of the Game Boy. He was brought on board to R&D1 (the "Game Boy division" at Nintendo basically) to help Yokoi because he had more of a tech background. But Okada wanted to basically create a pocket Famicom/NES which was the more popular idea at Nintendo. This lead to a giant shouting match at one point where Yokoi finally reneged and agreed to let Okada basically take over as lead of the project.
- R&D2, basically the hardware division for the Famicom/Super Famicom (NES/SNES) though the Game Boy project was basically shit. It was outdated and the display was crap in their view. They were petty enough to even block Okada from contacting Ricoh, the manufacturer of the NES/SNES CPUs. They were busy with the SNES development and didn't want the handheld from getting any resources from Ricoh. Okada had to go with a Sharp CPU as a result (lol).
- The use of the monochromatic (green, non-color basically) screen was extremely controversial even inside Nintendo at the time. Internally a lot of people at Nintendo felt the project with the non-color screen was an embarrassment, making light of the system's DMG codename (Dot Matrix Game) and calling it "Dame Game" in Japanese (translated roughly to "terrible game" in English) or "Damages" to mean that the product would damage Nintendo.
- Nintendo had cut a deal with Citizen (the Japanese watch maker) for the display. They were offered both a non-color monochrome screen and a more expensive color screen. They chose the monochrome, but at the last minute Yamauchi had a meeting with Sharp and agreed to let them be the screen supplier instead. Yokoi was so embarrassed/scared of having to tell Citizen that Nintendo had basically back stabbed them that he forced his subordinate Mr. Taki to do it. Taki was also afraid of doing it, so he basically told Citizen Nintendo would be using Sharp for now but making a color handheld in the future and made a fake tech document with specs for it (lol). But he ghosted Citizen's calls after that hoping they would leave him alone. The funny part is apparently Citizen took these fake docs to Sega and they made the Game Gear that had a lot of the design elements that Taki had made for the fake Nintendo color Game Boy, including having a color Citizen screen.
- The Game Boy was actually CANCELLED. Yeah you read that right. When hardware prototype was presented to Yamauchi in 1988, the contrast and viewing angles on the screen was so bad that Yamauchi cancelled the project immediately.
- Gunpei Yokoi was so down in the dumps about this that he actually became suicidal according to his biography. He felt like Yamauchi was being influenced by other Nintendo divisions who were shitting on the project and trying to sabotage it. Remember Yokoi had been with the company a lot longer than most of the video game guys, he had designed a bunch of toys that had been Nintendo's bread and butter sales in the 1970s long before Mario or Donkey Kong ever came around.
- R&D1 was assigned to other projects after the Game Boy was canned but Yokoi and Taki continued to work on the project in secret.
- 3 months later, fortune had shifted for the R&D1 Game Boy team. It turned out the Super Famicom/SNES had to be delayed and couldn't make it's release date, which I guess was actually supposed to be 1989? Nintendo needed something new to sell and Yokoi brought Yamauchi a more updated version of the Game Boy that had fixed some of the viewing angle issues. Yamauchi in another Mr. Burns like change of heart decided to fast track the system into production to make up for the SNES delay.
Pretty interesting how Nintendo's internal divisions basically all hated each other (lol) and the "father" of the Game Boy didn't really want to make the system it ultimately became. On top of that it was actually cancelled as a project direct from the president of Nintendo himself, haha. Nintendo of the 80s/90s was some wild shit, drama all the time.