In fourth episode of the first season, Sam arrives at Castle Black, forced to join the Night's Watch after his father bluntly tells him that if Sam refuses, the he'd kill Sam and stage it as a hunting accident. The move to the brotherhood causes Sam to forfeit his rights as heir of House Tarly, but he concedes he'd rather take on the new adventure than bear further criticism from his father about his weight and scholastic interests.
Unfortunately, Sam is immediately pegged as a "pampered lord" by Master at Arms Alliser Thorne. The statement fuels the already harsh mocking from the other recruits who call Sam "Lady Piggy." Jon Snow steps in to defend Sam and a powerful friendship is born.