|“||Congratulations on finishing Very Hard mode! You've unlocked Shadow Kirby!”|
|— Kirby Fighters Deluxe|
Shadow Kirby is the clone of Kirby that exists in the mirror world, debuting in Kirby & The Amazing Mirror. He also appears in Kirby: Triple Deluxe as the final boss of the Kirby Fighters sub-game, and as an unlockable "palette" in Kirby Fighters Deluxe.
In Kirby & The Amazing Mirror, the original appearance of Shadow Kirby is like that of most members of the Kirby species, but colored dark gray with black feet. In Kirby: Squeak Squad, using "Shadow" paint on Kirby makes him look like Shadow Kirby.
In Kirby: Triple Deluxe, Shadow Kirby's eyes are pure white, and his skin is semi-transparent and an alien purple shade. Shadow Kirby's body visibly swirls about like a vortex.
At the beginning of the game, Kirby and Shadow Kirby believe each other to be enemies. Shadow Kirby appears once in each of the mirror world's areas to attack Kirby, and if Kirby defeats him in combat, he will drop a random power-up, such as an Invincibility Candy or a 1UP.
However, Kirby discovers Shadow Kirby wants his world to be saved just as much as Kirby wants his own world to be saved, so they ally with each other to take down the one true villain: Dark Mind.
During the fight with the final boss, Dark Mind, Shadow Kirby will appear if Kirby loses the Master Sword and throw it back to Kirby.
At the end of the game, it is revealed that the only reason Shadow Kirby attacked Kirby is that he just wanted to protect the mirror world and keep any foreign being out of it. Shadow Kirby decides to continue to protect the mirror world after Dark Mind is defeated just in case he returns. His relationship with Dark Meta Knight is not elaborated on.
When encountered, Shadow Kirby will jump out of hiding and proceed to attack Kirby by using a Copy Ability. If Shadow Kirby is not defeated within a short time limit, he will jump back into hiding and not reappear until the player re-enters the level. Notably, the Copy Abilities used by Shadow Kirby use the effects of their respective enemies. For example, when Shadow Kirby uses Fire, the fire stream produced will have the same appearance as that of the fire used by Hot Head.
Shadow Kirby appears as the seventh and final opponent of the Kirby Fighters sub-game when playing in single-player mode. He is fought in Another Dimension, and uses the same Copy Ability the player chose at the beginning of the mode. After being defeated, Shadow Kirby rises into the air and explodes.
Shadow Kirby reappears in Kirby Fighters Deluxe as an alternate skin for Kirby, unlocked by beating single-player mode on Very Hard difficulty once with any Copy Ability. The game treats Shadow Kirby solely as a cosmetic color scheme, and he no longer appears as a named adversary, with Team DDD replacing him as the final single-player opponent.
Shadow Kirby can use Copy Abilities just like Kirby. In Kirby & The Amazing Mirror, he does not wear hats to show what Copy Ability he has. In Kirby: Triple Deluxe, he will mirror the ability the player selected at the start of Kirby Fighters Deluxe by clearly wearing a cap.
- In Kirby & The Amazing Mirror, Kirby can inhale and swallow Shadow Kirby for a Copy Ability (which depends on the Copy Ability Shadow Kirby is using). However, he will later appear unharmed regardless of whether Kirby inhaled him or not. He shares this trait with other inhalable characters, such as Bandana Waddle Dee, who have a significant role in the story of Kirby games.
- It is unknown if the Shadow Kirby from the Kirby Fighters sub-game of Kirby: Triple Deluxe is the original Shadow Kirby, as he has a redesigned appearance and an entirely different role. He might be the same one, as there are other clear references to Kirby & The Amazing Mirror during Dededetour. However, as the character's role occurs outside the main story line, it remains uncertain.
- Shadow Kirby is seen cheering for Kirby and King Dedede in Kirby: Triple Deluxe's "Kirby Master" video.