Kirby's Return to Dream Land
Kirby's Return to Dream Land
There is a unused enemy in the game's data named Hearbell. It was originally going to eat and chew Kirby, much like another enemy in the game, Pacto. It's unknown why this enemy was removed in the final release.
Contributed by Ophl
Depending on the color the player chooses as Kirby, if they interact with one of the flowers, the flower will turn the same color as the Kirby being played.
Contributed by Ophl
When Kirby's Return to Dreamland was localized in Europe, the title name was changed to Kirby's Adventure Wii and has the same box art from the Japanese version, rather than the box art from the North American release.
Contributed by Ophl
In the final battle, a song called "Halberd" plays, but the Halberd is nowhere to be seen. It is possible that the song is a left over from when Metaknight wasn't considered to be a playable character.
Contributed by noobheadz
Some of Kirby's rock transformations reference Kirby characters from past games. An example of this is Marx, who also makes a cameo in the Kirby Master video.
Contributed by JelloBoyInc
An unused alternate design for the enemy Walf can be seen in the game's files. The early design is missing the blue cap, has a brighter shell color, a simpler eye, and no alternate facial expression textures.
Contributed by DeerBoarDude
There were originally going to be more Super Abilities. A Super Spark and Super Cutter were planned, but were cut for two reasons. The Super Spark data is completely overwritten with Ultra Sword files and the Super Cutter was cut due to it being to similar to Ultra Sword. The model and icon for the Super Cutter still remain on the game's disc.
Contributed by Bean101
The Instant Mega Blast uses the same key combination as Street Fighter's Hadouken, likely meant as a tribute to the series.
Contributed by UltimateAdrian20
Kirby's Return to Dream Land underwent an 11-year development cycle, perhaps one of the longest in the series. It started right after the release of Kirby 64: The Crystal Shards, designed for the GameCube. This project featured 2.5D visuals (similar to Kirby 64), co-op multiplayer, was tentatively titled "Kirby GCN", and was one of 3 canceled projects.

The second one was in a fully 3D environment, yet had not achieved the quality Nintendo had expected. The third one was once again a 2D side-scroller with pop-up book visuals. These projects were eventually recognized as failures due to how most of the focus was on multiplayer instead of the game itself.
Contributed by game4brains
The first letter of all the levels leading up to the final level spell out "Crowned":
• Cookie Country
• Raisin Ruins
• Onion Ocean
• White Wafers
• Nutty Noon
• Egg Engines
• Dangerous Dinner

This refers to the final boss, Spoiler:Magolor, as he uses the master crown in the final battle.
Contributed by DidYouKnowGaming