User blog comment:MarvelDCandFantasyFanBoy12/The Thing!/@comment-3004323-20201011234824/@comment-24839525-20201011235650

Secret:

Character: The Dark Samurai (voiced by Dante Basco) - a villainous version of Austin from an alternate dimension who attempted to replace him.

Episode: Dimension Split - Austin reluctantly works with Jerome after an evil version of Austin has made everyone believe that the real Austin is a clone.

Growgan:

Character: The Mind Mites (non-speaking) - a bunch of termites with mind controlling capabilities.

Episode: Mind Mites Attack - Growgan wakes up as everyone is acting weird as he tries to figure out why.

Game On:

Character: The Mist Queen (voiced by Linda Cardellini) - a mysterious siren who has been luring anybody who sees her into eternal servitude.

Episode: Mind Tricked - Sly, after seeing a mysterious woman, begins acting strange as [the other main] has to figure out why.

Igor:

Character: Victor (voiced by Steven Ogg) - a snobby vampire real estate agent who wants to take control of the castle.

Episode: Rowdy Helena - After drinking a strange juice, Helena starts acting weird as Igor investigates.