Mordecai: Dude, what are we going to do this weekend? Nothing's going on. Rigby: I don't know. Mordecai: (gasps) Dude, it's Benson! Muscle Man: (reminding Benson) Alright, so that's tonight. Don't forget it. Benson: We'll be there. Muscle Man: See you there. Mordecai: What was that all about? Rigby: I don't know. Pops: Oh, Mordecai and Rigby. What costumes are you going to wear? Mordecai and Rigby: Costumes? Benson: Muscle Man's throwing a birthday party for Hi Five Ghost. Apparently, it's a costume birthday party. Rigby: Let me see. Mordecai: Ah, what? It's invite only. Rigby: No, I did not. Rigby: Why?