Sludge

Sludge is a revolting mixture of unknown liquid and solid components serving as a hazard. It may slow Pikmin and leaders that tread through or touch it, and may even threaten the well-being of Pikmin affected by it if it has any noxious properties.

=In fanon games=

In Pikmin: Rise of the Plantae
Purple goop is a hazard in Pikmin: Rise of the Plantae. It pulls in and suffocates Pikmin that step into it, and only Purple Pikmin are immune to its effects. It is found at Dead G, and in Hysterical Tutorial and Squack Cavern.