When Penny invites the guys to her Halloween party in season 1, the costumes they wear cause confusion among the guests. Sheldon (as the Doppler Effect) is mistaken for a ''choo choo train,'' it's unclear whether Raj is Thor the Norse God of Thunder or Thor of Marvel's The Avengers, Howard's Robin Hood getup makes him look more like Peter Pan, and Penny's ex-boyfriend teases Leonard (dressed as Frodo from The Lord of the Rings) about being a dwarf. Of course…