Pipetto is a chemical mixing robot from Mega Man 11 who is exclusive to Acid Man's stage. It has the ability to shoot chemicals. If the chemical lands in a acid pool, it can change the color. While in some cases this will not be harmful, but if it turns green, it becomes corrosive and can harm Mega Man on contact (though having the Acid Barrier can protect Mega Man).
It is possible to prevent the acid pool from changing color by destroying the chemical shot. To make it easier to hit both Pipetto or it's chemical shot and bring them down quickly is with a Power Gear-enhanced Block Dropper or Tundra Storm.