From MUK's body seeps a foul fluid that gives off a nose-bendingly horrible stench. Just one drop of this POKéMON's body fluid can turn a pool stagnant and rancid.
Sapphire:
This POKéMON's favorite food is anything that is repugnantly filthy. In dirty towns where people think nothing of throwing away litter on the streets, MUK are certain to gather.
Fire Red:
It is usually undetectable because it blends in with the ground. Touching it can cause terrible poisoning.
Leaf Green:
Thickly covered with a filthy, vile sludge. It is so toxic, even its footprints contain poison.