Fanon: Many fans assume the embarrassing Christmas photo is the photo Squidward took of SpongeBob in the episode "Christmas Who?" Another theory exists that it's a photo that was taken during one of Nickelodeon's "Nickmas" holiday bumpers.
Tear Jerker: "It's the best friends forever! Best friends forever! Ring!" SpongeBob has to use their friendship ring to prove to Patrick that it's him and not an intruder. Patrick breaks down crying because it means SpongeBob has betrayed his trust, which was why he refused to believe it was really him until that point. And the little figures of Spongebob and Patrick on the ring are so darn cute...
Catharsis Factor: One of the major reasons for its enduring popularity, as the increasing levels of cosmically unjust torture Squidward suffers in the shows Seasonal Rot only makes this episode grow more satisfying with age. For the first time in the entire series, Squidward actually won, his hard work pays off, everyone else pitches in to help him out, and Squilliam quite possibly suffers an abrupt heart attack and dies. This is a major part of the reason many fans consider it an unofficial series finale - it's a good way to end it off.
Squilliam apparently being so shocked by the band's performance that he suffers a heart attack on the field and is carried off by paramedics. Then again, he totally had it coming.
Ensemble Dark Horse: Debuting in one of the best-received, if not the best-received Nicktoons episodes ever would most likely have granted Squilliam this honor by default, but he's gone on to be one of the show's most popular supporting characters, if nothing else then certainly due to the fact that episodes he appears in usually end in victories for Squidward.
Fridge Brilliance: SpongeBob mentioning that time Larry overdosed on tanning pills explains why Larry, an uncooked lobster, is red.
"Funny Aneurysm" Moment: The scene where the two flag twirlers twirl their flags so fast they get propelled, crash into a blimp, and die. This episode first aired on September 7, 2001, just four days before 9/11.
The whole episode, from the sheer incompetency of the Bikini Bottomites at playing their instruments, to the hilariously dark blimp death, and to SpongeBob's "eager" face.
The German dub, when SpongeBob takes over conducting, has him saying the line, "Eins, und zwei, und keine schlägerei!" ("One, and two, and no brawls!"), as though he expects one to happen again.
The part where Sandy stuffs Patrick into a trombone. From Patrick's over-the-top scream, to the way everyone just blankly stares at him without even changing expression, to the trombone sounds when he walks, every second of that scene is side-splittingly hilarious.
Hype Backlash: The sheer amount of the praise of the episode has caused this for some people, with many of those detractors describing the episode as "overrated".