Koopa Land- This is the first World that Wario and Waluigi go to. The boss is yellow toad.
Toadworth's Body- After Wario and Waluigi beat Yellow Toad, Toady Potter shrinks them and Toadsworth eats them. Since Toadsworth doesn't want Wario and Waluigi in his body, Blue Toad shrinks himself and meets the Wario Bros on Toadsworth's skin.
Sky Land- The boss here is Red Toad.
Desert Land- The boss here is Green Toad.
Dessert Land- The boss here is Orange Toad.
Forest Land- The boss here is Purple Toad.
Ocean Land- The boss here is Toadette.
Mushroom Kingdom- Toadsowrht is the Boss here.