Foongus appears to be based on a mushroom and a Poké Ball.
Foongus' name may come from fool and fungi. Also, if the names of Foongus and its evolved form, Amoonguss, are put together, it sounds like the phrase "Fungus among us."
Foongus is the fourth Pokémon to resemble a Poké Ball, the others being Voltorb,Electrode, and its evolved form. However, unlike the others, it only has a Poké Ball design on it, instead of being in the shape of one.