A Thugglet slug is a rose red colored Uncommon Psychic Slug with small horns, a mohawk, and mask patterns over the eyes. They have illusionary abilities that only affect living things as seen in "The New Kid: Parts 1&2". When they transform, horns grow, their body turns skinny and they grow large teeth. The only one seen belonged to Twist but was a Ghoul pretending to be a normal Slug.
A famous Thugglet (Ghoul pretending to be a slug) is Loki, who belongs to Twist.