- Squidward Tentacles
- Squidward's Bonsai (debut; cameo)
- SpongeBob SquarePants
- Patrick Star
- Flying Dutchman (debut; cameo)
- Fish in the magazine
- Sandy Cheeks (cameo)
- Eugene H. Krabs (cameo)
- Clay (cameo)
- Jennifer Millie (cameo)
- Jimmy Gus (cameo)
- Nancy Suzy Fish
- Tina Fran
- Seagulls (debut)
Squidward is proud of having just finished his wax sculpture of himself and declares he has "conquered all artistic medium." But then, he is annoyed by SpongeBob and Patrick, who are playing a very loud game. When Squidward goes to take a bath, SpongeBob and Patrick begin to toss around a shell as a Frisbee, but it flies into Squidward's house and hits the wax sculpture. SpongeBob and Patrick think they've injured Squidward, and after several humorous attempts to "resuscitate" him, they believe that Squidward died.
Squidward, fresh from his pampered bath, dramatically emerges in a rush of steam from the warm bathroom, wearing talcum powder and a white bathrobe and towel. SpongeBob and Patrick believe they are seeing Squidward's "ghost" and, hoping to avoid any haunting or punishments, place themselves as Squidward's willing servants. Squidward gleefully takes advantage of the situation, having them serve and pamper him, do chores, and simply entertain him.
Eventually, SpongeBob and Patrick are instructed to clean out one of Squidward's "messy" rooms. Upon cleaning, they come across a comic book inspired by the story of the Flying Dutchman (who haunted the seas because his body was used as a window display in a clothing store and was never put to rest), and decide that since Squidward is a vengeful spirit, and they have to put Squidward to rest. SpongeBob and Patrick try to get Squidward to go into a casket, but he refuses. SpongeBob and Patrick then try to give him a proper burial as well as a funeral. Squidward eventually admits his charade, but SpongeBob and Patrick believe that Squidward is simply in denial about his death. SpongeBob blows a giant bubble that engulfs Squidward and sends him floating up to "the great beyond" truly sending him out of the water and high in the air with a flock of seagulls.
|( ‣ ) Associated production music|
|( • ) Original music|
|( ◦ ) SpongeBob music|
‣ Tales from the Swamp (a) - Ron Goodwin [title card]
‣ Smoke and Dreams - Otto Sieben [opening]
‣ Grass Skirts Blowing - Jan Rap [SpongeBob and Patrick playing games]
‣ Bossa Cubana - Gerhard Narholz [Squidward takes a bath]
‣ Gator - Steve Belfer [tossing a shell back, forth]
‣ Lovely Scenery (c) - Mladen Franko [Squidward's statue melted]
‣ Bossa Cubana - Gerhard Narholz [Squidward putting on a towel]
‣ Dangerous (a) - Mladen Franko [putting the statue back together]
‣ Dramatic Cue (h) - Ronald Hanmer [eyes turn over]
‣ Deep Grief 1 - Otto Sieben ["He's pushing up daisies!"]
‣ Tales from the Swamp (a) - Ron Goodwin [Squidward comes out of the bathroom]
‣ Dramatic Cue (d) - Ronald Hanmer ["Look what you've done to me!"]
‣ In the Crypt - Dave Hewson ["Enough! Listen up!"]
‣ Tales from the Swamp (c) - Ron Goodwin [end of Squidward's speech]
‣ Seaweed - Steve Belfer [taking Squidward outside]
‣ The Rake Hornpipe - Robert Alexander White [feeding Squidward]
‣ Stack of Leis - Kapono Beamer [night passes]
‣ In the Crypt - Dave Hewson ["What's this? Napping on the job?"]
‣ The Achterhoek Dances - Jan Rap [cleaning the back room]
‣ In the Cradle (b) - Dick Stephen Walter [comic book about Flying Dutchman]
‣ Gator - Steve Belfer [putting Squidward to rest]
‣ Funeral Music - Alfred Kluten [the mourners]
‣ Hawaiian Happiness - Jon Jelmer [Squidward confesses]
‣ Vibe Link (b) - Richard Myhill ["Patrick, say that again."]
‣ Queen's Aloha Oe (c) - Kapono Beamer, Queen Lili'uokalani [ending]
- As of January 29, 2017, The Internet Movie Database (IMDB) gives this episode a rating of 8.7/10 based on 331 ratings by users. TV.com users give this episode a rating of 8.7/10 based on 196 votes.
- "Squidward the Unfriendly Ghost" was ranked #95 during the Best Day Ever event on November 9–10, 2006.
- This episode marks the first appearance of the Flying Dutchman, although, he is only seen in pictures and does not physically appear. His first live appearance is in the Halloween episode "Scaredy Pants."
- This is one of the seven episodes in which the 1986 Paramount Pictures logo is plastered with the 2002 Paramount logo. The others are "Help Wanted," "Squeaky Boots," "F.U.N.," "Employee of the Month," "Karate Choppers," and "Rock Bottom."
- When SpongeBob says G7, the chord is played on a ukulele.
- When SpongeBob and Patrick attempt to revive the sculpted replica of Squidward that they believe is him, Patrick says he knows what to do and attempts to give him CPR. Patrick uses CPR to revive Squidward after he falls unconscious from choking in the episode "Naughty Nautical Neighbors."
- This and "Sandy's Rocket" are the only episodes where Squidward's house is depicted with an elevator in it.
- When Squidward gives SpongeBob a piece of tissue paper and asks that he plays a song with it, SpongeBob refuses, saying he cannot. However, in the episode "The Paper," SpongeBob is shown to be able to replicate the notes of a clarinet perfectly with a gum wrapper. It is possible that SpongeBob was too afraid of Squidward's "ghost" to bring proper music to the paper when he actually attempted to play a song with it or because it was a piece of tissue instead of a candy wrapper.
- As revealed in this episode, it is possible that Patrick suffers from Absence Seizures. Absence Seizures are characterized as suddenly zoning out and having consciousness interrupted momentarily. While the symptoms vary from patient to patient, common traits generally involve having glazed eyes, having speech interrupted for a few seconds, and remaining transfixed in place. After a few seconds, the patient will resume what they were doing without any memory that they had a seizure in the first place. Patrick, when saying the line "I know a lot about head injuries, believe..." exhibits all of these common symptoms.
- Because of Patrick's comment on how he "knows a lot about head injuries," it is possible that the cause of his low intelligence is due to a past head injury not seen in any other episodes. Evidence of this can be seen in the episode "Big Pink Loser," where Patrick says he has been hitting himself on the head with a hammer "way before I started copying [SpongeBob]."
- On the October 22, 2015 airing, this episode was paired up with "Ghost Host."
- This episode premiered on Mark Hamill's 48th birthday.
- This episode possibly takes place after "Bubblestand" because SpongeBob learned to blow bubbles in that episode and in this episode he knows how to make bubble art.
- In the French Dub, this episode is called "Le Fantôme de Carlo" which means "The Ghost of Squidward."
- This is Fred's 10th appearance.
- During the scene when Patrick and SpongeBob are carrying Squidward around in servitude to him, with Squidward complaining it is "too hot" or "too wet," they stumble onto an aquatic version of the painting La Troupe de Mlle. Eglantine. Squidward quips that it is "Too loose, Lautrec," a pun on the name of the painting's artist, Henri de Toulouse-Lautrec, with an accompanying rim shot.
- The painting is also named Troupe de Poisson, play on the painting La Troupe de Mlle.
- The episode's name is a parody of Casper the Friendly Ghost.
- When Squidward asks, "What are you invertebrates doing?," SpongeBob and Patrick seem to have made up a nonsensical game having to do with chess boards, bubbles, and rocks. SpongeBob and Patrick answer, "We don't know." This may be a reference to Calvinball, a game played in the comic strip Calvin and Hobbes.
- When Squidward is on the royal bed, SpongeBob's house is missing.
- In the Filipino dub, SpongeBob says, "Not buried properly" instead of "Never put to rest."
- After Patrick says, "I think they make a cream for that now," Squidward's face powder is missing throughout the entire episode.
- Squidward is seen in a bubble towards the end of the episode, even though bubbles are filled with air and "air is not good" for sea creatures.
- Since he is shown to be alive in later episodes, it's possible he managed to escape at some point.
- When SpongeBob and Patrick enter Squidward's house to retrieve the shell, they exit from the lift to Squidward's room. Additionally, Squidward's door has a different appearance. In other episodes, the appearance of his door is different from how it's depicted in this episode.
- When SpongeBob says "Never mind," his eyelashes are missing.
- Before Squidward goes to check if SpongeBob had played music for him, SpongeBob's arms are at the bottom of his pants. However, when Squidward says, "You're supposed to be making music for me," his arms are on the sides.
- When Mr. Krabs says "We all came when we were sure you were dead," his white undershirt is gone. It then returns again.
- When Squidward says, "Now get rid of that tombstone and tell all your friends to go home!" to SpongeBob, the mourners go home, but the tombstone remains.
- When SpongeBob is running to the green coral, the shell is never seen lying near the coral.
- When Squidward shouts, "Hey," a small white bubble is seen for a split second on the left side of the screen.
- The rock SpongeBob throws doesn't appear to be broken after he and Patrick try to figure out what to do next.