During his time at Hogwarts, he became good friends with three other boys his age: James Potter, Sirius Black, and Peter Pettigrew. These four came to be known as the Marauders, infamous for their mischievous antics. They knew Hogwarts and the grounds like the back of their hands, and actually created a magical map that showed the location of everyone on the grounds and in the castle. The map also revealed the many secret passages hidden in the school. His friends knew of his lycanthropy, but did not seem to mind. They simply referred to it as his "furry little problem". Later on, they even became Animagi (a person that can turn into an animal) so that they could accompany him on the full moon and make his transformations more fun.