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 is dead.
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 hauntings 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, while entering a "messy" room, 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, SpongeBob and Patrick think they need to have Squidward to be put 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".
As of October 29, 2013, The Internet Movie Database (IMDB) gives this episode a rating of 7.6/10 based on 113 ratings by users. TV.com users give this episode a 8.7/10 based on 181 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 seen only in pictures and does not physically appear. His first live appearance was in the Halloween episode "Scaredy Pants".
When SpongeBob says G7, the chord is played on a ukulele.
This and Sandy's Rocket are the only episodes where Squidward's house is depicted with an elevator in it.
When Squidward asks, "What are you invertebrates doing?" SpongeBob and Patrick seem to have made up a nonsensical game having to do with (presumably among other things) chess boards, bubbles and rocks. SpongeBob and Patrick say, "We don't know". This may be a reference to Calvinball, a game played in the comic strip Calvin and Hobbes.
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.
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 rimshot.
The episode's name is a parody of "Casper the Friendly Ghost".
When Squidward is on the royal bed, SpongeBob's house is missing.
After Patrick says "I think they make a cream for that now", Squidward's face powder is missing.
Squidward was in a bubble, even though bubbles are filled with air and "air is not good" for sea creatures.
When SpongeBob and Patrick enters Squidward's house to retrieve the shell, they exit from the lift to Squidward's room. Squidward's door has also a different appearance. In other episodes, the appearance of the door is different. And also, the lift also never appears in other episodes.
When SpongeBob said "Never mind!" his eyelashes are missing.
Before Squidward was going to check if SpongeBob had played music for him, SpongeBob's arms are at the bottom of his pants. But when Squidward says, "You're suppose to be making music for me." his arm are on the sides.