Backgammon (Famicom Disk System)
This game has hidden developer credits.
The FDS Backgammon is an adaptation of the popular board game which was supervised by the Japan Backgammon Association. It also features a song by Dragon Quest composer Koichi Sugiyama, who is also the honorary chairman of the Association.
CaH4e3 discovered a lot of secrets in this game, they should be documented.
At the ending screen, after the stamping animation is complete, wait for exactly three minutes. Then, hold Left + Down + Select + A on Controller 1 and Right + B + A on Controller 2. The code won't work after 30 seconds, and any incorrect input will return the player to the title screen.