The Sleeping ghost  (Also known as Slumber ghost)  is a blue ghost that spends an eternity trying to find a place to rest.   It eventually took refuge in a California movie studio.
20 years after an undisclosed incident in Studio 9, a trap door is reopened by two workers.  This trap door is located at a set once used to film the "Deadly Dr. Crowley" movie classics. The noise from the filming of the action film, "Space Avengers of the Galaxy" awoke the ghost and it possessed the star set piece, the Megazoid. It then caused the Megazoid to change its facial appearance into a monstrosity. The ghost then chasing after the Ghostbusters and destroyed anything that produced noise.
Egon became convinced the only way to stop it was to use Sign Language to communicate.  Egon would persuade the ghost to come with them and they would provide a place for it to sleep in peace, the Containment Unit. Everything was going smoothly until the loud mouth director of Space Avengers come bursting in to protect the $2 million Megazoid. This caused the ghost to return to an agitated state and it almost returned to the Megazoid. The Ghostbusters were able to capture and trap it.
Due to the fact that a sleeping ghost's primary objective is eternal slumber, disturbing them puts them in a grumpy and nasty mood.
- In storyboards, the ghost was depicted holding a blanket and wearing a night cap and sleep mask.
- On page 31 of Ghostbusters Annual 2018, in panel 1, a ghost is based on the Sleeping ghost, when it first woke.
- NOW Comics Vol. 1-17
- He also appeared in an issue of the NOW comic book series where he tells Samhain to stop chanting because he needs some sleep, though his appearance is drastically altered. He is now colored red and has legs. Despite the differences, he still bears some similarities to the way he appeared on the show.
- ↑ Egon Spengler (2009). The Real Ghostbusters- Take Two (1986) (DVD ts. 16:04-16:07). Time Life Entertainment. Egon says: "According to these readings, it was a Sleeping Ghost."
- ↑ Egon Spengler (2009). The Real Ghostbusters- Take Two (1986) (DVD ts. 16:08-16:15). Time Life Entertainment. Egon says: "Certain kinds of ghosts spend an eternity looking for a nice quiet place to sleep. When they're awakened, they're very cranky."
- ↑ Sleeping ghost (2009). The Real Ghostbusters - "Take Two" (1986) (DVD ts. 10:17-10:18). Time Life Entertainment. Sleeping ghost says: "Will you be quiet?"
- ↑ Crewman (2009). The Real Ghostbusters - "Take Two" (1986) (DVD ts. 07:10-07:16). Time Life Entertainment. Crewman says: "Yeah, but it hasn't been opened in 20 years since that accident back in..."
- ↑ Ray Stantz (2009). The Real Ghostbusters- Take Two (1986) (DVD ts. 20:11-20:16). Time Life Entertainment. Ray says: "He's using sign language. That way he doesn't have to make any noise."
- ↑ Egon Spengler (2009). The Real Ghostbusters - "Take Two" (1986) (DVD ts. 11:03-11:07). Time Life Entertainment. Egon says: "Peter, I think you should know I'm getting very high readings off that thing."