Mr. X

Mr. X (ミスターエックス) is a fake persona of Dr. Wily's, which he used to mask his true identity in Mega Man 6. Mr. X is a mysterious billionaire of unknown origin that is the leader of the X Foundation. He financially supports the World Robot Alliance and is the sponsor of the 1st Annual Robot Tournament. In the beginning of Mega Man 6, he takes control of eight of the strongest Robot Masters in the final event of the tournament to help him conquer the world. Before being revealed to be Dr. Wily in disguise, Mr. X mentioned that he was the one who manipulated Dr. Wily into helping him take over the world.

X Crusher
Mr. X fights with a iron ball type machine called X Crusher (Ｘクラッシャー) that swings in the screen and shoots a purple ball that splits in two when it touches the floor, each part sliding a different direction. Mr. X seems to have motion sickness while using it. When the machine is destroyed, he flies out from it and reveals that he is really Dr. Wily before escaping to his Wily Castle.

Strategy
Stay to one side and attack it by using any weapon (Flame Blast is it's weakness). Dodge the energy balls by jumping. A good strategy is to use a charge shot.

Trivia

 * Just before unmasking himself, Mr. X cries out: "My plan for world domination has faild". This typo was fixed in the Mega Man: Anniversary Collection.
 * Mister X is commonly used as a pseudonym for someone whose name is secret or unknown.