The Curious Factory
The Curious Factory is the first level of the Ruby Passage from the Game Boy Advance Wario Land 4. It is a labyrinth of a factory with robot-like enemies and many machines called Compressors and Decompressors, which turn Wario into Flat Wario and back again. Most of the flooring and platforms in the level is made up of conveyor belts. The enemy Kaentsubo first appears in this level. The Kaentsubo's heads are on fire, and when they get close to Wario, he will transform into Flaming Wario and will be able to break Bonfire Blocks. Hitting the Frog Switch will open up the underground area of the level, which is more challenging than the upper level.
Trivia
This level's music can be found in the WarioWare Inc.: Minigame Mania minigame Paper Plane without the machinery sounds.