Barbie Fairytopia Mermaidia is where he first appears, as the leader of the Fungi. He threatens to pour a bottle of Laverna's magical poison into the ocean to destroy Mermaidia if Prince Nalu does not lead them to the immunity berry.
In Barbie Fairytopia Magic of the Rainbow, he stalks Azura and later Elina under Laverna's orders. He is later turned into a toad to stand in for Laverna, so the guardians think she is still in exile. He is then brought back to the crystal palace where he spits venom at Guardians of Fairytopia making them unconscious.
Fungus Maximus has dark green skin and hazel eyes. He wears a purple suit, a gold ring with a purple gem on his left middle finger, and has many warts on his face. His ears are pointed and his nose takes up most of his face.