This is the most well-known "S3E13" involving ghosts. It is a meta-episodic parody presented as a pilot for a reality TV show called Ghostfacers .
: Sam and Dean Winchester accidentally end up in the middle of a reality show investigation of the "haunted" Morton House. [S3E13] Ghosts
: During a Halloween train ride, a mysterious, cold little girl visits Hanna's mother, Ashley, at home. This girl is heavily implied to be a spirit, likely referencing the twin story Alison told in earlier seasons. Celebrity Ghost Stories (Season 3, Episode 13) This is the most well-known "S3E13" involving ghosts
The story for varies significantly depending on which TV series you are referring to, as several shows have an episode with this exact designation or title. Supernatural (Season 3, Episode 13: " Ghostfacers ") : During a Halloween train ride, a mysterious,
: The amateur "Ghostfacers" team—Ed, Harry, Spruce, Maggy, and Corbett—gets trapped during a supernatural "lockdown". One of their members, Corbett, is killed by the ghost of a lonely survivalist named Freeman Daggett.
The series finale for the Netflix run of this sitcom used the title "Ghosts" metaphorically.