- Sludge has a normal consistency in terms of movement. It behaves the same as Water, Cold Sludge and Hot Sludge. Sludge is needed to complete all Doofenshmirtz Evil Incorporated levels and to collect Evil Gnomes. If it enters Perry's or an Agent's pipe, the level is failed. Sludge will also kill both Water Gnomes and Steam Gnomes.
- Reactions with Fluids
- Notable Reactions with Objects