Ending is the ending theme from Mega Man 3 and Proto Man's theme, composed by Yasuaki Fujita. A remix appears in Proto Man's ending from Mega Man: The Power Battle and Mega Man 2: The Power Fighters, as ProtoMan.EXE's theme in Rockman.EXE 4.5 Real Operation (titled Theme of Blues), and in We are ROCK-MEN!.
In the Mega Man comic book series by Archie Comics, Proto Man made the tune himself, while in the manga Mega Man Gigamix this is a melody that Proto Man heard and liked. In the Rockman 5 manga and Rockman Battle & Chase manhua, Proto Man uses a flute instead of whistling.
- The music only plays for 1 minute and 12 seconds in Mega Man 3, but players can hear it whole (2 minutes and 7 seconds, plus looping) by holding Up and A on controller 2 at the ending cutscene as Mega Man teleports from Dr. Light's Laboratory.