In 1991 Sunsoft released Blaster Master Boy (BMB), for the Game Boy audience in the U.S. In Europe, Sunsoft re-titled the game "Blaster Master Jr.". BMB/BM Jr. was unique, in that players were forced to use Jason only: Sophia the 3rd was removed from this game (Sunsoft worked this in by stating in ads that only Jason could fit into the narrow underground tunnels). In the game players used bombs instead of grenades, although Jason still had a gun. Jason now needed lamps for dark rooms, stilt shoes to walk over spikes, and lifesavers to get across water. There were also powerups such as energy pills, megabombs, and armor powerups that gave Jason more protection against enemy hits.

A visitor to BMUG, Sean Howard, pointed out that BMB is not really a BM game at all, and there is a distinct reason why it looks and plays so much like a Bomberman game.

"Don't know if you knew this, but in Japan, Blaster Master Boy was called Bomber King 2. A sequal to Bomber King for the NES. I think it was released here as Robowarrior by Jaleco.

Anyway, Bomber King was part of the Bomberman series, designed to be more adult to appeal to mech lovers. Anyway, just thought you'd like to know that Blaster Master Boy was originally a Bomberman game."

So in reality, Blaster Master Boy is actually based on the game package used by Bomber King 2 (BK2). BK2 was produced and released in Japan by Aicom Co. Ltd. for the Game Boy (not surprisingly, this is the same company credited for the development of Blaster Master Boy). The only difference is the title screen: everything else is a dead ringer for BMB. It even retains the same cheat code (move bubble over Continue, press A+START and select any period/stage you want).

It could be speculated that since the main character looks like Jason from BM, and to cut down production time, all would be needed is to create a new title screen, box and manual. With this, Sunsoft had very quickly added another title to the BM line-up.