Development Hell: Between Kirby's Air Ride and Kirby's Return to Dream Land (Epic Yarn was developed by Good Feel instead), HAL Laboratories made repeated attempts to create a home console game for the Kirby series. Their most known attempt was the GameCube game, announced in 2004, and widely believed to be reincarnated as Kirby's Return to Dream Land. However, an interview revealed that the GameCube game was only the first of four attempts at a home console game, the final being Return to Dream Land.
Kirby Air Ride itself was trapped in Development Hell for quite some time. It was originally intended as a Nintendo 64 game, but after spending many years in production, it was quietly canceled. It finally showed up as a GameCube title at E3 2003.
Executive Meddling: Rumor has it that Masahiro Sakurai left HAL because this happened during the development of Air Ride.
And he also didn't like the sequelization of the gaming industry.
Fan Nickname: King Dedede is sometimes referred to as "DDD", "Triple-D", or "3D".
The bandana wearing Waddle Dee that served as Dedede's right hand in Super Star Ultra was referred to as Bandana Dee, which Nintendo made canon in Triple Deluxe.
No Export for You: One Kirby spin-off game called "Kaabii no kirakira kizzu" (Kirby's Super Star Stacker) for the SNES (Super Famicon in Japan) never got released outside of Japan due to being released there in 1998 two years after the Nintendo 64's release.
For less known reasons, the 20th anniversary compilation-game Dream Collection didn't get a Europe or Australian release.
Throw It In: Kirby's appearance was originally intended to be a placeholder.
Urban Legend of Zelda / Word of Dante: No, despite what Mushroom Kingdom Fusion may have told you, 02 did not make any sort of "pact" with Drawcia. Nor is Dark Nebula 02 under another name. The latter theory has been officially Jossed by the Dream Collection Encyclopedia (though it does state that Dark Nebula is part of the same species as Dark Matter). Meta Knight also wasn't possessed by anyone during the events of Kirby Super Star.
Kirby Pink or Yellow: Some time during Kirby's Dream Land's development Shigeru Miyamoto made the suggestion to Masahiro Sakurai that Kirby be yellow instead of pink, since Miyamoto had little, if any, involvement in the games' development since Kirby is developed by HAL Laboratory while Miyamoto works for Nintendo's EAD division, this could have only have been a suggestion. However, to honor Miyamoto's suggestion yellow Kirby is usually the 2nd playerpalette swap for Kirby in his multiplayer appearances including the Super Smash Bros. series.
The Incredible Shrinking Kirby: Kirby was going to have a shrinking ability in Kirby's Adventure, but it was scrapped in favor of the UFO powerup. The mechanic was later used in Kirby and the Amazing Mirror.
Air Ride Stardom: Kirby Air Ride was supposed to have a multi-themed star shaped track, that got scrapped due to time constraints.
It was also supposed to have a much bigger city trial. The project was really ambitious even for its time. No wonder it took years to develop.
Prince Fluff's Epic Yarn: Prince Fluff was originally going to be the protagonist of Epic Yarn, before Fluff's Yarn got the Kirby label.
Meta Knight of Death and Rebirth: The artbook bundled with Kirby's Dream Collection includes unused character designs for some of the characters. Most notable is Meta Knight with red and black butterfly wings◊, rather than his purple bat wings.
Vaporware: Kirby, with the addition of a pink, curly hair on his head, was originally supposed to star in a Spinoff Babies game, Kid Kirby, for the SNES; it was never finished, and all that remains of the game now are a few sprites and one stage layout.
Air Ride began on the Nintendo 64 and was scheduled for a late 1996 release. It went through years of delays until it was quietly cancelled in 1998. It caught the public by surprise when a GameCube version was announced in 2003.
When the Nintendo 64 was in development and still called the Ultra 64, one title in development was Kirby Bowl 64 — Kirby Bowl being the Japanese name for Kirby's Dream Course. The snowboarding mode it featured likely led to Kirby's Air Ride as described above.
Also, Kirby's Tilt 'n' Tumble 2 for the GameCube, using the Game Boy Advance and cable to control the same way as the original title.
There were several attempts to make a console Kirby game for the GameCube and later the Wii. The first of such attempts was shown in an E3 trailer, but this one fell through. The fourth attempt was finally released on the Wii as Kirby's Return to Dream Land.