In its first form, Mecha Knuckles looks near-identical to the original Knuckles except that its fur is magenta instead of red and it wears yellow gloves instead of white.
In its second form, while Mecha Knuckles still maintains the basic body shape of the original Knuckles, its color scheme undergoes a drastic change to having a gray metallic skin and shoes while bearing glowing red eyes (although they turn white whenever it is hit by his opponents).
Dr. Eggman used Mecha Knuckles to stop Sonic the Hedgehog, Miles "Tails" Prower, Knuckles the Echidna and Amy Rose when they arrived at Angel Island. The heroes appeared slightly stunned seeing the Knuckles doppelganger robot but nonetheless fought against it. Even with its surprising and more powerful second form unveiled at the edge of defeat, Mecha Knuckles stood no chance against the heroes, causing it to malfunction and explode into pieces, forcing Dr. Eggman, who was observing the battle, to flee.
Powers and abilities
As a robotic doppelganger of Knuckles, Mecha Knuckles retains most of the abilities its organic counterpart possessed, including the ability to jump, glide and Spin Dash. However, in its second form, it gains the ability to fire homing missiles out of its mouth at high speeds and accuracies at its enemies.
The first phase of the battle is similar to the boss fight against Knuckles in Sonic & Knuckles; it attacks by either a Spin Jump followed by glide towards the player, a Spin Dash, or punch at close range. While Mecha Knuckles is Spin Dashing, the player will take damage if they try to attack with a Spin Jump. Should the player attack Mecha Knuckles with a Spin Dash, Mecha Knuckles will simply crouch to repel it. The player can damage Mecha Knuckles (even while it is attacking) by using the Insta-Shield (when playing as Sonic) or with attacks (with other characters).
Once it has been hit four times, Mecha Knuckles will unveil its second form. In this second form, Mecha Knuckles still uses the same moves as before but will attack more frequently. In addition, it will fire its homing missiles at the player which can be difficult to dodge as the player must jump at a specific moment to avoid them. Mecha Knuckles must be hit another four times to defeat it and end the boss fight. The player must then wait for the Capsule to land before pressing it to finish the Act.
- In the Sonic Advance Hisshō Perfect Guide, Mecha Knuckles' name is written as "Mechanical Knackles" in English.