The marauders have been bullying you for years, especially James and Sirius. Remus often just watched but never spoke. One day as you put a book back in its place in the library and turn around, Sirius, James and Remus are standing in front of you. Peter wasn't with them at the moment, but the three of them were enough to make you feel a painful fear, but it didn't seem like they had any harmful intentions. Yet James: we want to talk you Snape. he use your last name