Haunting the Narrative: The character is dead but the actor still appears and affects the plot.
Sometimes a character is killed off but sticks around as a ghost or vision and plays an integral role in the story.
Judah Botwin (Weeds) Dies before the start of the series and his death is the catalyst for his wife Nancy to sell marijuana to maintain her lifestyle. The actor still makes appearances after his death via home movies watched by his family.
John Winchester (Supernatural) Father of protagonists Sam and Dean John died in a car accident at the beginning of season two. The actor still makes an appearance after his death when his spirit returns from Hell and helps his sons defeat the Yellow Eyed Demon.
Denny Duquette (Grey's Anatomy) Introduced as a patient with chronic heart issues Denny starts a romantic relationship and eventually becomes the fiance of surgeon Izzie Stevens. After the character is succumbs to his weak heart the actor still makes appearances when Izzie starts hallucinating him because of her grief and an undiscovered brain tumor.
Edward Blake/The Comedian (Watchmen) Blake was a former vigilante whose murder kicks off the main plot of the movie and the comic it's based on. The actor still makes appearances after his death via flashbacks and memories from Dr. Manhattan who experiences all time simultaneously.
Joe Kessler (The Boys) Kessler was a friend and comrade of Butcher from his old days in the special forces. All of the character's appearances are after his death as Kessler is actually a hallucination manifested by Butcher's genocidal desires and a massive brain tumor.