Twin Devil (ツインデビル Tsuin Debiru) is the boss of Wily Castle 3 in Mega Man 9. Like its Devil counterparts, it is composed of individual globs of jelly and a single eye. The jelly move around the screen, damaging the opponent on contact. Unlike other Devils, this is its only attack. However, the battle is made more difficult by the fact that the Twin Devil is actually two separate entities, one green sphere and one orange sphere. The sphere with the eye begins on the bottom right while the other begins in the top left. The globs break into 12 pieces and switch places one by one, some moving high, some moving low. After they have completely switched locations, they switch heights (the devil with the eye lowers and the devil without the eye rises). The only way to damage the Twin Devil is to damage the electronic eye as it moves between the two devils. It is difficult to damage the eye, but the Black Hole Bomb is extremely effective against the devil, and the nature of the weapon makes it very easy to hit.
- Twin Devil's eye bears a resemblance to the heads of Pantheon from the Zero series.
- Twin Devil is similar to Nightmare Mother from Mega Man X6.
- Twin Devil's two bodies are colored yellow and green, possibly as an homage to the Yellow Devil from the first Mega Man game, as well as the Green Devil from Mega Man 8 and Mega Man & Bass.
- Both Twin Devils appear in Archie Mega Man #55's Short Circuits.
|The "Devil" series robots|
| Yellow Devil • Yellow Devil MK-II • Yellow Devil MK-III • Black Yellow Devil • New Yellow Devil|
Green Devil • Twin Devil • Petit Devil Yellow • Petit Devil Green • Block Devil • Dark Moon • Grey Devil
Shadow Devil • Rainbow Devil • Lava Demon • "Steel Devil" • Chaos Devil