Brain Slug

Brain Slugs are little parasitic organisms who superficially resemble a type of semi-amorphous slugs. They attach themselves to the heads of intelligent beings (such as Humans) and control them so long as they are latched onto the subject's head. They are about as big as a fist, green, translucent and have two feelers and one enormous eye. They are not intelligent enough to be considered a galactic threat.

Symptoms of Possession
A person possessed by a Brain Slug will be likely to speak in a monotone voice and do everything to further the spreading of Brain Slugs throughout the universe, but the easiest way to tell a person is infected is by the brain slug sitting on their head. The recommended procedure of dealing with a brain slug victim is to act natural and switch to a garlic shampoo. Another way to deny attachment is wearing a helmet. Fortunately, Brain Slugs are not very intelligent, minimizing the risk. Once removed from the afflicted person's head, the person returns immediately to normal. It also seems that a brain slug will starve and die if the creature it is attached to is particularly stupid i.e. braindead.