Here’s a description of the episode,
Sam’S Bodysnatched! -- Gary (guest star Colton James), a teenage nerd, conjures up a body-switching spell and changes bodies with Sam (Jared Padalecki). Thrilled by his new handsome and built body, Gary (now Sam) investigates a case with Dean (Jensen Ackles) and takes advantage of his good looks and age by hitting on women and getting drunk. Meanwhile, Sam is stuck in Gary’s teenage body, dealing with intrusive parents and high school.