Okay, I love this movie, so I watch it a lot. Toward the end, when Charlie makes the deal with Red, he runs out of the house with Itchy on his heels. The doors open for him, but not for Itchy. Why? Because Itchy doesn't have a collar.

Fast forward to where they are fighting Red. When Itchy takes the horn from Red and starts running away, Red asks him if he wants the horn or his friends. It does a close up on Itchy while he is making a decision. Look around his neck. He has a collar on now. How did he get this one?