Amoonguss is a mushroom-like Pokémon that debuted in the fifth generation. Its cap resembles a Poké-Ball, so with the loss of Voltorb and Electrode in that generation, it and its pre-evolution act as the "fake item ball" pranksters. It also has shields for hands, which also resembles Poké-Balls. Since it's a mushroom, its one of the lucky few Pokémon that can learn the highly-coveted Spore.
It and its pre-evolution's English name likely derive from the phrase "there's a fungus among us".
All canon Pokémon are available to catch in Tropes vs. Women in Pokémon Training, including Amoonguss. Wherever it may be found, Amoonguss may sometimes take the form of fake item balls, as in Generation 5.
