Kirby Mass Attack

"You again?"

Because of this game, Daroach has had the most lines out of every Kirby character.
King Dedede is one of the objects which can be fished out of the water in the fishing sub-game that plays after the last level. He requires the most effort to fish out of all other possible items. Also, the slice of Strawberry Shortcake seen at the beginning and end of Kirby: Squeak Squad can be caught in the fishing sub-game.
Kirby Mass Attack references Kirby's original name, Popopo, as it takes place on the Popopo Islands.
Kirby Mass Attack is the last 2D sprite-based Kirby game without any polygonal 3D graphics.
Often when performing actions, or when entering doors while still eligible for a Gold Star, the mini-Kirbys shout "Poyo", which was a vocalization Kirby often repeated in place of actual speech in the anime, Kirby: Right Back at Ya!. This is among the few Kirby games where that is the case, as most other games where Kirby "talks" has him shouting variations of "Hi!"

In addition, the Sub-Games of Kirby Mass Attack feature a number of characters otherwise exclusive to the anime who make cameo appearances. These include Chef Shiitake, Max Flexer, Escargoon, Captain Waddle Doo, and the N.M.E. Sales Guy.

This is the only game in the series where Kirby can drown underwater (but can still breathe in space. Daroachy-poo points this out).
This game, Kirby 64: The Crystal Shards, and Kirby's Blowout Blast are the only Kirby platformers to not feature the Kirby Dance at the end of a stage. Kirby 64: The Crystal Shards only featured the theme, and Kirby Mass Attack is the exact opposite: it only features the dance on the "game over" screen of Kirby Brawlball. Kirby's Blowout Blast does not feature the dance at all.
This game has a very large amount of unused content left in the game's files.

The game's internal codename is wadogo, although filenames also use WADO frequently. The Japanese name for Waddle Dee is ワドルディ or wadorudi, with "wado" being a shortening of this name.
Additionally, a number of sound effects of Kirby's voice have internal names of SE_WANYA_DO, SE_WANYA_RE, SE_WANYA_MI, and so on up to SE_WANYA_HI_DO, suggesting that they may have been "wanya" vocalizations earlier in development (similar to the "wanya" vocalizations used in Kirby Brawlball for the Waddle Dee elements on the board).

Kirby Mass Attack is the third platformer in the Kirby series to lack Copy Abilities. The first two are Kirby's Dream Land and Kirby's Epic Yarn.

Similarly, this is the third platformer in which Kirby cannot inhale. The first two are Kirby: Canvas Curse and Kirby's Epic Yarn.

Kirby Mass Attack's game over screen may be a reference to the game over screen shown in Mother 2, another game produced by HAL Laboratory.