http://animal.discovery.com/news/briefs/20050912/tongueeater.html

“This crustacean is considered in the scientific community to be the first known case of a parasite that ˚actually replaces an organ of its host˚.” There’s a cognitive analog of this parasite amongst humans; but it doesn’t just replace your tongue — it goes after what moves it. It doesn’t look like an insect: it looks …like a famous person. The first symptom of infection is you parroting them.