In his fifth year, three out of the four Marauders attempted to prank Severus by having him wake up locked in the same room as Remus Lupin, a werewolf, on a full-moon. Although the prank was only meant to scare Severus, the pranksters were too late to try and pull him from the room, and Remus bit him. Afterwards the three Marauders were severely punished, but were not expelled like Severus had hoped, and he was sworn to secrecy about the incident. Although Remus was the one who bit him, he harbored no ill feelings towards the former Marauder, and the two actually became friends, bearing the transformations each month together.