It is often said that Wassies with 'shit for brains' are the ones with mushrooms growing out of their heads. This is not exactly true. Wassies which are host to mushrooms (fungus wassicus) do have normal Wassie brains but like all Wassies, there is an enormous empty space in the Wassies skull given the fact that the average Wassie brain is the size of a pea. These Wassies simply have dirt, decaying matter and potentially fecal remains in that cavity which encourages the growth of the mushroom.
The mushroom has a symbiotic relationship with the Wassie once it has rooted itself in the Wassie's skull, and removal of the mushroom will lead to the death of the Wassie. The Wassie provides a safe medium for the mushroom to take root and the mushroom provides the Wassie with a not-so-nifty camouflage in forested environment. The mushroom releases spores when the Wassie dies and the spores often find their way to the respawning Wassie so that the relationship can carry across Wassie lifetimes.
The mushroom is said to have psychedelic properties and Wassies which are host to these fungi have been known to be targeted by poachers, particularly in East Asia, who believe the fungi contain healing properties.
It is unknown whether the presence of the mushroom affects the Wassie's brain, personality or actions in anyway (like certain strains of cordyceps) given the fact that Wassies are inherently stupid and prone to acting in death-inducing manners regardless of the presence of a mushroom.
