| Pokedex Entries: |
| Red | Thickly covered with a filthy, vile sludge. It is so toxic, even its footprints contain poison. |
| Blue |
| Yellow | Smells so awful, it can cause fainting. Through degeneration, it lost its sense of smell. |
| Gold | They love to gather in smelly areas where sludge accumulates, making the stench around them worse. |
| Silver | Its body is made of a powerful poison. Touching it accidentally will cause a fever that requires bed rest. |
| Crystal | As it moves, a very strong poison leaks from it, making the ground there barren for three years. |
| Ruby | From MUK's body seeps a foul fluid that gives off a nose-bendingly horrid 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. |
| Emerald | It prefers warm and humid habitats. In the summertime, the toxic substances in its body intensify, making MUK reek like putrid kitchen garbage. |
| FireRed | It is usually undetectable because it blends in with the ground. Touching it can cause terrible poisoning. |
| LeafGreen | Thickly covered with a filthy, vile sludge. It is so toxic, even its footprints contain poison. |
| Diamond | A toxic fluid seeps from its body. The fluid instantly kills plants and trees on contact. |
| Pearl |
| Platinum | A toxic fluid seeps from its body. The fluid instantly kills plants and trees on contact. |
| Stadium 1 | Becomes indistinguishable if it hides in dirt. Touching its sludge-covered body causes horrible poisonings. |
| Stadium 2 | They love to gather in smelly areas where sludge accumulates, making the stench around them worse. |
| TCG | Dark Muk: Muks appear suddenly, spreading sludge everywhere. Whenever one appears in a city, panic ensues. |
