Duo

Duo (デューオ) is a character from the original Mega Man series. He is an extraterrestrial robot with the mission to eliminate the Evil Energy. His left hand glows to absorb and destroy the Evil Energy.

Duo chronologically first appeared in the beginning of Mega Man 8 fighting in space against a unknown evil robot with Evil Energy, and the two crashed in a island on Earth during the battle. Mega Man is sent by Dr. Light to investigate the island, where he finds, and takes the broken Duo to Dr. Light while Dr. Wily gets away with the Evil Energy. After Dr. Light starts to repair Duo, and after the defeat of the first four Robot Masters, Duo awakes and goes after the Evil Energy in Dr. Wily's hideout. There he finds, and fights against Mega Man thinking he is evil, before realizing he wasn't. He then joins forces with Mega Man, helping him against Dr. Wily, and later saving his life.

In the fighting game Mega Man 2: The Power Fighters, which was released before Mega Man 8, Duo is a playable character. In his ending of the game, he leaves Earth holding a unknown energy (believed to be Evil Energy remains from Mega Man 8), departing from Dr. Light and other playable character if the game was completed by two players. After this a text appear saying his story would be revealed in Mega Man 8.

Duo is also a playable character in Mega Man: Battle & Chase, Rockman Strategy and Rockman Gold Empire. He has cameo appearances in Mega Man & Bass as a data CD and in MegaMan Battle Network 2 as a poster in Lan Hikari's room. His Battle Network counterpart, Duo, is the last boss in MegaMan Battle Network 4.

Powers and abilities
Duo himself has greater strength than average robots. He has the ability to turn himself into a ball-like form to crush his opponents.

In Mega Man 2: The Power Fighters Duo has the ability to copy bosses powers like Mega Man, possibly this ability was given to him by Dr. Light.

Mega Man 8 voices
Attacks:
 * "Hya!"
 * "Get ready!"

Mega Man: Battle & Chase

 * Vehicle: Hard Grandeur
 * Body: Giga Fist Body
 * Engine: Final Engine
 * Wing: Maximum Wing
 * Tire: Supreme Tire

Mega Man & Bass CD data
A robot who has fought for universal peace. He came to earth looking for an evil energy.

I'm keeper of peace & justice.

Good point: Justice

Bad point: Busy

Like: Universal peace

Dislike: Villains

Japanese CD data:

Good point: Heart of justice

Bad point: Busy with duty

Like: Universal peace

Dislike: Villains 

Trivia

 * Duo is called "Dio" in Rockman Strategy.
 * In the first cutscene of Mega Man 8, when Duo is fighting the robot Wily got the evil energy from, his design is quite different from what is seen elsewhere. Though barely visible, except when Mega Man found him, the silhouette reveals the upper torso was different. However, the book R20 Rockman & Rockman X Official Complete Works has artwork of Duo in his original form. It is possible that most of his original body was destroyed and Dr. Light had to find replacement parts.