At one point, Mega Man 9 was going to be released on DS in addition to the Wii, But because the screen size of the DS is smaller than that of the Famicom, the idea was dropped.
For some reason, the word 'Sigma' is censored if you enter it at the player naming screen.
Contributed by DeerBoarDude
According to Capcom, there is a secret that no one has found in Mega Man 9. To this day, no one has any idea what the secret is, or if Capcom is telling the truth about it.
Contributed by gamemaster1991
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Bass, Mega Man's rival from "Mega Man & Bass", makes a cameo appearance on Dr. Wily's monitor in the ending cutscene.
Contributed by KnowledgeBase
According to the booklet of the Rockman 9 Arrange Album, Bass, known as Forte in Japan, was absent from the game because he was undergoing "adjustments" during the events of Mega Man 9.
Contributed by KnowledgeBase
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Both Splash woman and Hornet man had their genders swapped. Splash woman was named Ocean Man and Hornet man was named Honey Woman. The reason they were changed was because Inafune wanted the female robot master to be represented by a mermaid.
Contributed by gamemaster1991
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Chun Li from the Street Fighter series makes a cameo appearance as a newscaster in the introductory cutscene.
Contributed by Bean101
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Dr. Wily's Swiss bank account number (19-871-217) is a reference to the original Mega Man's Japanese release date, December 17th 1987 (19871217).
Contributed by DidYouKnowGaming