One of the enemies in Kirby Mass Attack, a cube-shaped tank, was not named in-game. On the 10th anniversary of the game in 2021, designer Takayuki Nakayama revealed that the character's name was "Crap". The name was likely derived from "scrap metal" rather than the mild English profanity (which would have guaranteed a name change during the English localization should the name have been used in-game).

After first appearing in a trailer for the cancelled Kirby GCN, HR-D3 made its official debut in Kirby Mass Attack. Its attacks and color scheme are virtually identical to those seen in the trailer, meaning the robot was likely included as a reference to the cancelled Kirby game. Despite this intentional reference, however, its laser is inaccurate; the laser HR-D3 fired in the Kirby GCN trailer was blue while the laser it fires in Kirby Mass Attack is orange.

In the minigame Kirby's Quest, Moto Shotzo and one of the bosses that Kirby flees from while riding a Moto Shotzo are from the gameboy game "Trax", another HAL Laboratory game that was made in 1991.

Unused files in the game's data suggests that it was originally possible to access a palette selection screen where the player would have been able to change the colors of the Kirbys, but it was scrapped for unknown reasons. It would have been possible to chose up to thirteen color palettes, with most of them corresponding to the Spray Paint colors in Kirby & the Amazing Mirror and Kirby: Squeak Squad.

In the Japanese version of Kirby Mass Attack, if the player gets a game over in the minigame Strato Patrol EOS the background is plain blue with the title "Holy Nightmare". In the English version, the background shows a person who looks similar to Nightmare. Both screens are a reference to the anime in the Japanese and 4kids dubs.

There are unused sprites of King Dedede in Kirby Mass Attack's memory. These sprites are shown from above, suggesting that he was intended to be a playable character in the Strato Patrol EOS sub-game at one point in development.

In the original Japanese version of Kirby: Squeak Squad, Spinni is referred to as female, but no mention of the character's gender is made in the game's English version, possibly to avoid any controversy with gender issues. However, the American version of Kirby Mass Attack refers to Spinni as male.

Escargoon, Chef Shataki and "Customer Service", 3 characters from the Kirby Anime, all make cameo appearances in some of the game's mini-games.

The logo for the "Kirby Quest" mini-game bears a striking resemblance to the logo of the RPG Arcana, released for the Super Nintendo in 1992, and also developed by HAL Laboratory.

The Design for King Dedede's Castle from the "Kirby: Right Back at Ya!" anime is reused in Kirby: Squeak Squad, Kirby's Epic Yarn & Kirby: Mass Attack, with Squeak Squad featuring the Monster Machine from the anime in the throne room.

In the Japanese version of the game, there is an enemy credit sequence that also featured Kirby having a picnic. While it was disabled in the other versions, the graphics can still be found in the game's files.

This game is set in the Popopo Islands, which is a reference to Kirby's original name, Popopo.