5 Box Art Mistakes - VG Facts Five Trivia Feat. JonTron
Super Smash Bros Wii U - Did You Know Gaming? Feat. Smash Bros Announcer Xander Mobus!
Assassin's Creed - Did You Know Gaming? Feat. Jake of Vsauce3
GameCube - Did You Know Gaming? Feat. SpaceHamster
Pikmin - Did You Know Gaming? Feat. JonTron
Although the GameCube Controller itself was well beloved by fans, head of Platinum Games (and former Capcom dev) Atsushi Inaba said it was actually quite frustrating to develop for for devs like him and he wasn't a big fan of it and it's layout and design.

"I didn’t play a lot of GameCube games myself, but on the development side of things you imagined that maybe when Miyamoto-san was designing his games, the large green A button was the one he wanted to get hit first so he made it big [...] When working on Viewtiful Joe, we made the A button the jump button but because it was an action game players wanted to punch and kick, so they would sometimes hit the A button expecting that. In development, you don’t want the player to pick up the controller with any kind of strange prejudices about which button is going to do what. It’s almost safer not to have too much imbalance with the buttons."

Inaba, however still praised the system's software and hardware, saying that it was very easy to develop games for the console itself.
Contributed by PirateGoofy
In the GameCube 20th anniversary VGC interview, it was revealed that former Nintendo of America VP of marketing Perrin Kaplan thought that there was one aspect of the GameCube that he and NoA were not fond of and made them extremely nervous about the console's perception:

"We actually suggested that the purple was not the best [console color] to start with and [Japan] said, ‘no, we’re going to use that [...] Then we pushed for black and silver, because I think in the US nobody had ever really done the purple colour before. [...] It wasn’t that you couldn’t bring out hardware that was a different colour, it was just a very… ‘female’ looking colour. It just didn’t feel masculine, I think. I remember us being very nervous at E3 that we were going to get bad press purely based on the colour.”

Nintendo of Europe was not to easy on the color either with the company's veteran Shelly Peirce revealing that one person referred to it as a "Fischer-Price record player". However Pierce remained optimistic because he felt that what Nintendo was doing was uniquely different than the competition.
Contributed by PirateGoofy
In an interview with VGC for The GameCubes's 20th anniversary, veteran Rare developer Martin Hollis revealed that not only was he among the first people to see "Project Dolphin", but also that he was possibly responsible for the GameCube's name and theme:

“I arrived in Kyoto, went into the big building, and Mr. Miyamoto and his team straight away took me to this empty meeting room and sat me down in front of a television [...] They switched it on, and Miyamoto told me to press the A button on the controller. I pressed it and the purple rolling cubes appeared on screen with the boot up music that we now know so well, revealing the GameCube name. [...] As the on-screen reveal happened, Mr. Miyamoto stared at my face intensely! That was my initiation, which was maybe because I’d actually suggested the name ‘Cube’ during my time at NTD. Months earlier I did a sheet of paper at Nintendo of America with a whole load of suggestions for names and one of them was ‘Star Cube’ or something like that.”

Nintendo did indeed trademark "Starcube" lending more legitimacy to Hollis' suspicion.
Contributed by PirateGoofy
At Spaceworld 2000, it was announced that a version of the Gamecube Memory Card that would have expandable memory via an SD card would be released. However, this never came to fruition.

A similar device that allowed for the plugging in of an SD card into memory card slot was released alongside Dobutsu no Mori e+ in Japan, however this was only to take screenshots and did not allow for the saving of game data.
Contributed by Takahashi2212
The original slogan for the GameCube, "The Nintendo Difference," was meant to distinguish Nintendo from its competitors as an entertainment company first and foremost.
Contributed by game4brains
According to former Nintendo president Hiroshi Yamauchi, the GameCube's cheap price was the result of Nintendo's perception that gamers cared only about the games themselves, and that game consoles were just pieces of hardware that were required to play the games. As a result, Nintendo decided to make the GameCube's price significantly lower than the competition's in order to make the former's titles more accessible to consumers.
Contributed by game4brains
The GameCube was the first Nintendo console to lack a launch title that starred Mario as the protagonist.
Contributed by game4brains
Nintendo had once patented and developed a prototype motion controller for the GameCube; this controller went so far into development that game developer Factor 5 experimented with them for potential use in their launch titles.
Contributed by game4brains
There exists a GameCube Service Disk that was used by the Nintendo World Class Service to test and diagnose problems with the console and peripherals. It is assumed that once Nintendo retired the World Class Service, they took back the disks and destroyed them, which would explain why there are very few ever found.

This disk contains a fair amount of unused content, from unused sounds and unused test pictures to stereoscopic 3D test pictures.
Contributed by SonicManEXE
The Panasonic Q was a version of the Nintendo GameCube that had the ability to play DVDs, audio CDs, and MP3s. The console ceased production after two years and only sold 100,000 units. One cause of the console's failure was that it was actually cheaper to buy a GameCube and a DVD Player separately.
Contributed by Pogue-Mahone
The GameCube controller's design possibly originated from a prototype controller for the Virtual Boy. They were both purple, and had a similar shape.
Contributed by Boyobmas
The GameCube is actually capable of rendering stereoscopic 3D. The GameCube was going to have an add-on that would attach to a TV and enable it to properly display 3D games. The first planned game for the add-on was Luigi's Mansion. The add-on was eventually cancelled as it would have cost more than the console itself.
Contributed by gamerofgames
Nintendo ran a contest to help promote the upcoming release of the GameCube called "What would YOU do for a Nintendo GameCube?" where fans were picked to perform stunts that they'd chosen themselves to win a GameCube, Game Boy Advance, a games package, and USD. Some of the acts which were picked by entrants were to paint Nintendo logos with their tongue, juggling three consoles whilst dressed as a game character, painting and shaving themselves to be a Pikmin, and eating a GameCube made of spam, chocolate syrup, and cat food.
Contributed by KnowledgeBase
Two of Nintendo's biggest franchises, Mario and The Legend of Zelda, have water-centric games on the Gamecube. Some have speculated this is somehow related to the GameCube's early project name "Dolphin".
When the GameCube was released, Nintendo targeted a 50 million sale goal by 2005, in order to compete with Sony and Microsoft. The consoles ended up only reaching 21.74 million units sold (estimate).
Contributed by ThisGuyInTheSuit
The GameCube's SDK has strings that reference all of the known N64 peripherals, including obscure ones such as the keyboard and mouse, suggesting that the GameCube was once planned to have support for Nintendo 64 peripherals.
Contributed by xianc78
Before it was released, a tech demo for the Gamecube was developed which featured an explorable version of Princess Peach's castle. This demo was later leaked online.
Contributed by DokemonStudios
The working title for the GameCube was the Dolphin. As a result, many games from the GameCube era reference this, such as Super Mario Sunshine's setting being in the shape of a dolphin (the island is also named Isle Delfino; "Delfino" is Italian for "Dolphin") and Captain Olimar's ship in Pikmin being named the S.S. Dolphin. The GPU of the machine is named "Flipper", another reference to the console's codename.
Contributed by lividd3ad
The soft reflections used for the GameCube's startup animation and menu are the same texture file that Ocarina of Time and Majora's Mask use for shiny items.
Contributed by SonicManEXE
There are two hidden alternate start-up sounds which can play after you power-up the console. The first one features a squeaking sound and a child's laughter, which plays when you have a controller in port 1 with the "Z" button hold down as you power-up. The second is of Japanese instruments played which activates via the same method but instead with four controllers.
Contributed by natogamer583
There is a microscopic image of a Dolphin within a computer chip inside the GameCube, referencing the GameCube's codename during development.
Contributed by Dazz
The GameCube's BIOS menu has slow, seemingly random ambient background music.

This background music, when sped up to sixteen times its normal speed, is actually the intro jingle for the Famicom Disk System, a Famicom add-on released by Nintendo in 1986.
Contributed by Vipershark