Apothecary Gary made his only appearance in the episode segment "Children of the Spore" as the main antagonist. Prior to the events of the episode segment, Apothecary Gary took control of a local frog named Lloyd. He later encountered Hop Pop and tricked him to having a jar of elixir that would make Anne, Sprig, and Polly behave better. However, unbeknownst to Hop Pop, the "elixir" is actually a concoction of mind-control spores.
Slowly, the spores took over Anne, Sprig, Polly, and the rest of the Wartwood residence (except for Hop Pop and Bessie). After revealing his true self and motive, Gary battled Hop Pop in Bessie's stable. Eventually, Gary was eaten alive by Bessie after she ate the rest of his mushrooms, despite his pleads that his species would become extinct. Despite this, some of his spores survived and took control of Hop Pop's beetle Jeremy, which grew another mushroom resembling Gary.
Apothecary Gary, in his fungus form, resembles a large purple mushroom with light blue spots. His host's eyes turn bright purple with light pink pupils.
- Gary's species seems to be based on the amphibian (Batrachochytrium dendrobatidis) and salamander (Batrachochytrium salamandrivorans) chytrid fungi, both of which causes the disease Chytridiomycosis in amphibians; as well as entomopathogenic fungi that controls their victims' brains and sprouts out of their bodies.
- Apothecary Gary is the first major character (excluding the dangerous wildlife) in the series to not be an amphibian but rather an inorganic being.
- He is also the first major Amphibia character to die on screen.