Wikipedia
Sree Muthappan is a folk Hindu deity commonly worshiped in the North Malabar region of Kerala and Coorg region of Karnataka, India. Muthappan and Thiruvappan are considered to be manifestations of Shiva and Vishnu respectively.
Worship of Muthappan is unique in that it does not follow the Satvic Brahminical form of worship, as in other Hindu temples of Kerala. The main mode of worship is via a ritual enactment of Muthappan, performed daily at the Parassinikadavu temple. Fish and toddy is used as an offering to Muthappan, and people of all castes, religions and nationalities are permitted to enter the temple and take part in the worship.
Muthappan is the principal deity in the ritualistic Theyyam dance (Muthappan Theyyam) performed in the famous Parassinikkadavu temple. The ritual performers of Muthappan Theyyam belong to the Vannan community of Kerala. The puja rituals and rites for Muthappan are performed by the Thiyya community.