If you insert the Game Boy Advance game Kessakusen! Ganbare Goemon 1+2 while you have Goemon DS inserted in your Nintendo DS, when you start up the game, additional characters from the GBA game will appear in the DS game for you to talk to! In addition to this, a new mini-game called "Space Manbo" will be unlocked in the main menu of Goemon DS.
However, both of these unlockables will only remain in the game when Kessakusen! Ganbare Goemon 1+2 is in the GBA slot. Add