Unlockable: New costumes
Get all 30 elephants.

Goemon GBA Link-Up Bonus
Turn off your DS and put Kessakusen! Ganbare Goemon 1+2 for Game Boy Advance into the GBA slot and the DS Goemon game into the DS slot. Turn on your DS and start the DS Goemon game. The GBA game acts as a dongle that unlocks the following things:
New characters: NPCs from the GBA titles appear throughout the DS adventure
Space Mambo: This sidescrolling shooter is accessible from the mini-game menu as long as the GBA cart is inserted