If you say that "you guys are a bunch of sheep" that can mean two things:Originally Posted by Csilla Bagyi
-they are afraid to speak up for themselves, afraid to come forward and say what's on their minds. They are shy, meekish, vulnerable or they simply act cowardly.
-sheep ( other than the animal itself) also means a person lacking intelligence or common sense. Same as knucklehead, airhead, etc.
As for the first category, I think the word "follower" would be the closest and possibly a "tagalong".