Okay, everyone else has said it already, but ... I love how you can't tell if any of this is actually happening outside of Bill's head. Charlie's "Because you just wouldn't be you without a bit of jealousy behind your balls, would you?" sets the stage for that beautifully, as well as the possibility that Charlie might fuck Bill's wife (or make it look like he might be fucking Bill's wife) as a rough way of sort of playing with Bill.