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 .
: Penelope meets her ex-boyfriend Max at a wedding and realizes she is truly happy being single. Meanwhile, Elena confronts her father about their relationship. The episode concludes with Penelope officially becoming a certified nurse practitioner. [S3E13] Ghosts
The series finale for the Netflix run of this sitcom used the title "Ghosts" metaphorically. This is the most well-known "S3E13" involving ghosts
: Sam and Dean Winchester accidentally end up in the middle of a reality show investigation of the "haunted" Morton House. : Sam and Dean Winchester accidentally end up
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 ")