shadow friend
A friend that nobody really likes. You don't know where he/she came from and they try to weasle their way into your group activities. Most of the time nobody wants to hang out with this person alone. Usually characterized by a unusual or weird incident at a key point in deciding friendship. This person sometimes has no soul and little personality.
"Johns so weird, where did he come from and why does he think hes our friend?"
"Yeah, it would be cool if he didnt pass out while we were all having a good time. Hes such a shadow friend."
"Yeah, it would be cool if he didnt pass out while we were all having a good time. Hes such a shadow friend."