Making his debut in the episode "Band Geeks", Squilliam FancysonIII is a very wealthy, self-serving, unibrow-endowed octopus. He met Squidward Tentacles in high school band class and became his rival. Squilliam has succeeded in everything Squidward has failed in and thus looks down upon his rival. Squidward is painfully jealous and wishes to prove to Squilliam that he is not a loser.
Like other octopus characters, Squilliam's character model is nearly identical to Squidward's, but he has a unibrow and wears a fancy maroon robe. He owns a private yacht, a private lake, a private heliport, a private island, and a balloon/casino. He owns a fancy tower which made an appearance in "House Fancy."
Squilliam is an octopus with six tentacles. He wears a red and black robe and has an ascot. Squilliam has a large black single eyebrow, or unibrow. In "Band Geeks," he shows pride in it when he calls it "big and valuable." In "Professor Squidward," this feature is how the police told him apart from Squidward. In "House Fancy," Squilliam has a large replica of his unibrow that is made entirely out of gilded doorknobs.
Squilliam is rich and fancy. He makes no secret that he considers himself superior to others due to his enormous wealth. He is mean, selfish, sadistic, and arrogant, and takes great pleasure in asserting his perceived superiority over middle-class citizens like his arch-rival Squidward. He also speaks in a very mocking tone, placing great emphasis on his low regard for Squidward and an equally large amount of inflated praise in his lavish lifestyle. Even though he is a jerk, he somehow makes friends easily, probably for letting people in his private jet, yacht, and balloon/casino.
Squilliam is narcissistic and considers himself to be undeniably handsome, even though he and Squidward (and most other octopus characters) look alike, save for the unibrow. Squidward and Squilliam absolutely hate each other because Squilliam brags about everything he succeeds in to Squidward (which Squidward usually fails in) and is always mocking him for being of lower class.
Squilliam has appeared in six episodes. Additionally, alternate versions of Squilliam appear twice: a slave version of him from the Man Ray timeline appears in "Back to the Past," and he makes a cameo as one of Squidward's nose options in "Code Yellow."
He plays a major role in three episodes: "Band Geeks," "Squilliam Returns," and "House Fancy." He has not appeared in person since the season 7 episode "Keep Bikini Bottom Beautiful."
Squilliam's first appearance was in this episode. He challenges Squidward to play his band at the Bubble Bowl, as his own band could not make it. However, at the end of the episode, Squilliam arrives at the Bubble Bowl anyway to watch Squidward fail (which may imply that he was just setting up Squidward to make a fool of himself), but upon seeing the band's surprisingly good performance, Squilliam appears to have a heart attack and is rushed to the hospital on a stretcher.
Squidward tells Squilliam that he is the owner of a five-star restaurant in an attempt to show him up. Although Squilliam is initially impressed by SpongeBob's newfound fine dining expertise, Squidward is ultimately humiliated when SpongeBob cannot remember his own name and goes insane and destroys the restaurant. When Squidward tells the truth, Squilliam seems to confess that he lied about his life to show up Squidward, only to reveal that he was just joking and takes everyone for a ride in his balloon/casino.
Squilliam's ridiculously luxurious house is featured on the TV show of the same name. The house features, among other things, a golden toilet, an elevator with a built-in hot tub, and a massive sculpture of his unibrow made entirely out of gilded doorknobs. Squidward's jealousy once again gets the better of him when he calls the show's host, Nicholas Withers, claiming that his house is better than Squilliam's. Although Squidward's house is destroyed as a result of his attempts to make it fancier, Withers sees his destroyed house as a work of art and proclaims it to be better than Squilliam's. Squilliam breaks down and falls over, in tears, as he is once again upstaged by Squidward.
In "Professor Squidward," he is shown to be so highly admired and respected by everyone, that he was going to be offered a job as a music teacher at the Bikini Bottom Prestigious Music College. However, Squidward claims to be him so that he can teach the class himself. The real Squilliam then shows up and has Squidward arrested.
Squilliam also appears at the end of "I ♥ Dancing," where after Squidward is given the part of a line dancer for Squilliam, he begins to abusively train him in the same manner that Squidward did to SpongeBob.
In an alternate timeline, SpongeBob and Patrick from the original timeline walk by him putting up a sign in Bikini Bottom when Man Ray took over. This is so far the last time he appears and only time he appears without Squidward.
Squilliam makes a cameo as one of the many noses SpongeBob offers Squidward while operating on him.
"Sounds as though you've got a dying animal to attend to, eh old chum?"
"I'm filthy stinkin' rich!"
"It's a gilded doorknob."
"Come on everyone; let's go take a ride in my balloon slash casino!"
(referring to his unibrow) "It's big and valuable. I'm a leader of a big fancy band right now. And we're supposed to play the Bubble Bowl next week."
"Squidward Tentacles has the fanciest restaurant in Bikini Bottom, and he does not suck eggs (After Squidward tricks him into thinking he actually does own a 5-star restaurant)."
"Explain what? That you, Squidward Tentacles, voted most likely to suck eggs in high school, (walks into Krusty Krab) are trying to pass off a lousy burger stand as a five-star... (Gulps) ...restaurant!?"