Mushroom Mayhem

From the Super Mario Wiki

The Mushroom Mayhem is the first level in Mario vs. Donkey Kong 2: March of the Minis. It is realatively easy, as this is where the Mini-Marios' and Mario's adventure starts. The only enemies in the world are Mini-Shy Guys, Piranha Plants, and Toss Kongs. In the background of the levels, Toadstool Castle can be seen. Later in the game, Toadstool Castle appears as a level. The music played in the various levels of Mushroom Mayhem are remixes of the Mini Mario Levels from Mario Vs. Donkey Kong.