He started life as a little boring stick figure in a hi-tech computer. But one day, the computer went slightly haywire, sucking in a fully energized light-bulb and a computer chip, which collided with the stick figure into a creating machine, which brought Captain 0 to life. After scientists discovered his truly awesome powers, he was entered in a fighting stadium, fighting his way to the top of the fighting ring to become the Master Champion. After beating the first Master Champion, Captain 0 became known as one of the greatest fighters who ever lived. He went a-top the UnRank Scales to receive a hardy Roundhouse Kick from Chuck Norris himself, the one thing no one survives. It came, and it went. Captain 0 was left with no internal or external damages, his metal exterior wasn't even warped by the blow. He was then was bestowed the title of Undefeatable, and the rest was history.
He has powers similar to that of Matt from that Wii boxing shame, but has tougher fist power. He can also jump 30 feet high and run fast (almost as fast as Sonic himself). He also has another cool power, turn his own hands into Mega Man's beam cannon, and can use them with different abilities like a standard blaster, a highly nuclear flamethrower to burn down metal, or the powers of a Gravity gun or pocket blaster.
He owns the 5th highest UnRank, which is infinity x infinity.
He was originally have his own name be 0, but due to name confusions with Zero (or his revival form, Zero Two), he decided to change his name to Captain 0 so he'd be more recognized.
He is one of the few guys (along with the Undefeatable, Guiyii, Giygas, etc.) to be immune to Weegee's stare, because if Weegee tried to stare at him, he'd just sock him in the face and send him flying off a cliff.