Piston

The Compressor is an object in the Wario Land series. In the games, when Wario walks under one, the Compressor squishes Wario and changes his form to Flat Wario. Despite its effects, they do not harm Wario or any enemy in any sort of way. These objects mainly appear in factory levels. There is always a Recompressor that makes Wario back to his normal size.

Compressors also appear in Yoshi's Story in the level Mecha Castle. They appear in pairs and try to crush an unsuspecting Yoshi passing between. If a Yoshi is crushed he immediatly loses all the petals on the flower representing his health.