Anticlimax Boss: Some gamers felt Dark Nebula was a rather disappointing final boss in both story and gameplay. It's easier than almost every boss before it, having extremely predictable and easily avoidable attacks and a low amount of HP. Even if you somehow manage to lose the Triple Star ability before you reach it, beating with no ability at all is a simple task.
While the game is a bit of a contention point for most Kirby fans, many admit to really liking Spinni, thanks to being a Badass Adorableninja mouse.
Daroach, the leader of the Squeak Squad, is also popular. His popularity would lead to the Squeak Squad returning in Kirby Mass Attack as allies.
Game-Breaker: Tornado is overpowered to the point of literal insanity. You are effectively invincible while using it, you fly with easy controls while using it, it lasts forever, does absurd contact damage, and the kicker? The frame it ends, you can start another tornado. Quite possibly the most definitively broken power in the history of Kirby.
Hilarious in Hindsight: There's an enemy called Uja that looks like a black Master Hand made out of a swarm of insects that can also turn into a sword. Then in the fourth Super Smash Bros. game, we get the Final Boss, Master Core...
Idiot Plot: The Excuse Plot gets more nonsensical later on in the game. Once Kirby confuses the chest with his cake in it for the one Meta Knight is guarding, does Meta Knight sit Kirby down and explain things? No! He makes off with it, and Kirby starts chasing after him! Five minutes of rational conversation would've completely shut down the last section of the game.
Underused Game Mechanic: The mixing system can create unique abilities that can't be gotten by any other means. Too bad there's only five abilities that can be gotten this way, the items needed to make them are located in the last third of the game, and they're nothing more than elemental versions of Sword and Bomb, providing little extra combat advantage. It's basically a watered-down version of Kirby 64: The Crystal Shards' ability combination system.
The upcoming Kirby: Star Allies builds upon both mechanics. The abilities aren't as watered down as Squeak Squad, but they're slightly more limited as Kirby 64.