If been re-watching some Gintama episodes and noticed the parasitic mushrooms in some episode. Which started to grow on their head and slowly take them over.
I also came across the pokemon Paras to which something pretty similar happens:
While Paras' symbiotic relationship with the mushrooms on its back isn't exactly normal, it is beneficial for both; Paras feeds the mushrooms with its body, and the fungus provides additional means of defense. Exactly how much control the mushrooms can exert over the Pokemon isn't clear, but odd goes to disturbing when Paras evolves into Parasect.
It's hard to say exactly what change takes place at Level 24, but for some reason, the mushrooms take their chance and merge into a single organism, taking over the Paras in the process. With heightened aggression and a pair of zombified milky eyes, anything cute or endearing about Paras is replaced by a demonic drone known as Parasect.
So now my question: where does the parasitic mushroom come from? Is this made up in anime, or like allot of other anime components based on some kind of folk lore?