Insana
An Insana is a person everybody knows about. He is somebody who is always there among your group, but is not friends with anybody in particular. Everybody in the group finds the Insana creepy and disturbing, yet are unsure of how to proceed. Insanas are known for their ragged facial hair, grimy skin, and bad sense of humor. Most Insanas can latch onto another person for months or even years.
Just because we're in the same Latin class doesn't mean Chris should follow me around all the time. I'm getting the feeling he might be an Insana.