Kirby's Return to Dreamland (cancelled prototypes to Wii platformer; 2000-2011)
On October 24th, 2011, the game Kirby's Return to Dreamland, was released on the Wii. Interestingly, this game took elements from three other Kirby games that got cancelled during development.
Kirby Adventure (the First Cancelled Game)
The first cancelled game was announced at E3 2005 for the Nintendo GameCube under the tentative title Kirby Adventure. According to the footage that was released, it appeared to play similarly like Kirby 64. By having a 3D environment while being only limited to a horizontal path. It also originally had a four-player Co-op mode, in the style of Kirby Super Star, where Kirby can (after gains gaining a copy ability) either summon the enemy that had said copy ability (by pressing an undistinguished button on the controller), or a second, third, or fourth player could join in by gaining the copy ability that Kirby currently has. It also would've marked the first appearance of the Water copy ability which did eventually make its way into Kirby's Return to Dreamland. However, the reason the game got canned was that of the developers not achieving the level of quality they wanted.
The Second & Third Cancelled Games, + The Final Outcome
However, a Kirby game called Hoshi no Kābī (translated from Japanese to Kirby of the Stars) did appear on a list of upcoming Wii games set for release in Japan in 2006, and from time to time, appeared, and disappeared on/from other game lists as well. Then, Matt Casamassina of IGN furthered the idea of it appearing on the Wii stating it would be announced, and indeed be released on said console in 2007. Also, even though it wasn't announced at E3 2007, Beth Llewelyn of Nintendo of America did confirm that the project had not been abandoned. Back onto the other two cancelled games, the second cancelled game was originally going to take a more open-world style gameplay idea which would have been a huge first for the series, but due to extremely challenging gameplay, and the same reason as last time they cancelled a Kirby game, it was scrapped.
The third cancelled game would've returned Kirby to his side-scrolling roots, yet it would be in the graphical style of a Pop-Up Book, but it got cancelled for unknown reasons. Short after, the development team realized something: their ideas weren't working because they were focusing too much on 4-player mode and decided to strive for a 1-Player romp.
When Shinya Kumazaki was brought into the development team, he looked at the three cancelled games, took elements from it, threw those elements and the new ideas into the new Kirby's Return to Dreamland. It was finally re-announced, demonstrated and released in 2011. Even with their previous troubles with the solo mode, they instead were successfully able to get a 4-player Kirby game, while still making it feel like a 1-player Kirby game.
It is currently unknown if the three original betas still exist. However, in a 2011 Iwata Asks interview about Kirby's Return to Dream Land, three screenshots of each beta were shown, so it could be likely that the betas still exist, or if they were simply just photos of gameplay taken during development.