Note: This game is also titled Slime MoriMori: Dragon Quest 2 - Daisensha To Shippo Dan.
Knightro Slime tank in Challenge modeGo inside the church and press Y, L(2), Y, R(2), Y, Up, Down, Select to unlock the Knightro tank in Challenge mode.
The Nemesis Slime in Challenge modeGo inside the church and press Y, R(2), Up, L(2), L, Y, Down(3), Y, Select to unlock The Nemesis tank in Challenge mode.
Giggles in Tank Masters modeSuccessfully complete the game. Then, talk to "Meggan", the green Egg Slime in the northwest building of the central part of town.
Gott Schliemen in Tank Masters modeDefeat the final Boss and rescue all 100 Slimes. Then, defeat Hooly and the Shogun in the last round of Tank Masters mode to unlock Gott Schliemen in Tank Masters mode.
Schwarzen in Tank Masters modeDefeat the final Boss. Then, go to where you defeated Slival on Mt. Krakatroda. Defeat Slival again to unlock Schwarzen in Tank Masters mode.