Lots of foils here. The obvious one is Ros and Guil, but we go into that when we talk about the Protagonist and his Companion. Another one might be Guil and Hamlet, or Ros and Hamlet for that matter. The way the characters interact in this play defines them. As for Guil and the Player, they are both looking for a sense of control, but the Player is much more successful at finding it. He's like Guil, but more fun to hang out with and not so angst-y. Guil's need to question everything finds its counterpart in the Player's need to have an audience. The two appear to be opposed, but the longer you examine their oppositions, the more you see how they're alike.