Mega Man IV, known as Rockman World 4 (ロックマンワールド４) in Japan, marks the fourth game in the classic Mega Man series to be released on the original Game Boy. Mega Man IV follows the general pattern of previous Game Boy titles, combining content from existing NES titles with unique content and features. As with the previous Game Boy entries, the Robot Masters are taken from two different NES titles, with the first four taken from Mega Man 4, while the latter four come from Mega Man 5. Also following this pattern, the first four Robot Masters must be defeated before the second set of four can be accessed. Beat also appears, able to be called for assistance once Mega Man has obtained the B, E, A, and T plates found in the levels of the first four Robot Masters.