When destructive attacks by powerful robots begin occurring all over the world, Mega Man's creator, the good-hearted Dr. Light, is blamed.

Defeating each stage's "Robot Master" boss copies its unique weapon, which the player can select at will throughout the remainder of the game.

Although the game was developed for modern consoles, Mega Man 9 features familiar 8-bit visuals and audio similar to the Nintendo Entertainment System (NES) as a "retro" throwback to the earliest entries in the franchise.

Dr. Light, the creator of the world's greatest android hero Mega Man, is blamed when several old and outdated models of "Robot Masters" he created suddenly go on a destructive rampage.

Mega Man 9 is an action-platform game in which the player controls the titular character and must complete a number of 2D side-scrolling stages.

[6][7] Within each stage, the player advances by running, jumping, avoiding traps, shooting enemies and mini-bosses, and ultimately battling the Robot Master boss at the end.

[7] The player also begins the game with the option to call on Mega Man's dog Rush, who can transform into a "Coil" springboard for jumping higher or a "Jet" for traversing long distances in the air.

[14] Mega Man's health, his special weapons, and his Rush options are all limited by energy gauges that can be refilled by picking up items found throughout each level.

[6][7][15] Aside from using or omitting various elements from past games in the series, Mega Man 9 introduces a time attack mode and 50 optional challenges where certain requirements should be met to be accomplished.

[17][18] This downloadable content was included in Mega Man Legacy Collection 2, requiring the player to complete the game or enter a secret cheat code.

As early as 2004, Inafune, credited as "Inafking", publicly expressed his desire to make a Mega Man 9 as a "throwback to the super old school", but that its creation would highly depend on the input of fans.

He also believed that pushing for the creation of a Mega Man in the style of the original "would be quickly criticized for things like being simplistic, outdated, or too expensive", thus making it too difficult to develop such games in the current climate.

[6] Inafune cited the rise of retrogaming services like Nintendo's Virtual Console for allowing the development team to put together Mega Man 9.

As the team had a tendency to make these attributes complex, Inafune would often scold them to simplify their work and "bring it back to the basics".

The game includes a "Legacy Mode" option, which emulates the low video processing power of the NES by partially rendering sprites, thus causing them to flicker when too many are on screen simultaneously.

[18][27] The musical score and sound effects for Mega Man 9 were composed by Ippo Yamada, Ryo Kawakami, Yu Shimoda, and Hiroki Isogai.

[28] Yamada, a veteran composer for Capcom at this point, worked "with a sense of nostalgia", while the younger designers had to study and imitate the older games.

[29] Sound director Yu Shimoda analyzed the audio of the NES Mega Man games for several months before beginning the project.

[28] Still, as a spiritual successor to Mega Man 2, layers of background music were deliberately designed to drop out when simultaneously heard with certain sound effects as they did in that game.

[6][32] It was initially slated to be exclusive to WiiWare, with earlier reports of Microsoft's XBLA and Sony's PSN editions being denied by Capcom.

[36] T-shirts bearing the artwork were created for Inafune and Takeshita to wear at the game's official debut at the Electronic Entertainment Expo during the summer of 2008.

Being as faithful to the original 1987 release as possible, the iam8bit crew disassembled one-thousand vintage NES cartridges and inserted mini CDs inside.

[38] To help promote the game in Japan, Capcom released merchandise including "E-Tank" energy drinks and two CD soundtracks.

[40][41] The soundtrack, consisting of the game's 35 music tracks, includes a booklet with liner notes written by the Inti Creates sound team, as well as artwork and information on the eight Robot Masters.

[59][60] Although no financial figures for Mega Man 9 have been released, Christian Svensson (Capcom's Vice President of Business Development) debunked all sales rumors shortly after its launch, stating that the company was "cautiously optimistic" about its performance on WiiWare.