Mega Man: Dr. Wily's Revenge, known as Rockman World (ロックマンワールド ) in Japan, is the first Mega Man entry in the Mega Man World series for the Game Boy in 1991. The game recycles content from the original Mega Man for NES and its sequel, Mega Man 2. At the start of the game, only four Robot Master stages are available to choose, all of which are from Mega Man. The second four Robot Masters, all of which are from Mega Man 2, are fought as bosses in the Wily Castle. This would become a staple of the Game Boy games until Mega Man V, the only Mega Man game for Game Boy not to recycle large amounts of content from the NES games.