- Abigail Marge
- Harold "Bill" Reginald
- Squidward Tentacles
- Debbie Rechid
- Nathiel Waters (normal; purple)
- Tina Fran
- SpongeBob SquarePants
- Sea slug (mentioned)
- Eugene H. Krabs
- Sheldon J. Plankton
- Frank the Red-Shirt-Wearing Fish
- Nancy Suzy Fish
- Vera Fishbowl
- Karen Plankton
- Betsy Krabs
- Frankie Billy
- Miss Rechid
- Jimmy Gus
- Jennifer Millie
- Old Man Jenkins
- Frank the Lifeguard
- Male Judge
- Medley Fishbowl
- Nat Peterson
- Perry (teal)
- Sheldon the Fish
- Shelly Fishbowl
- Susie Rechid
- Martha Smith
- Lion Fish (debut)
- Frank the Goldfish
- Patrick Star
- Gladiator (debut)
- Popeye fish (Blue)
- Monroe Timmy
- Norma Rechid
- Jellyfish (mentioned)
- Whale (mentioned)
Plankton decides to destroy the Chum Bucket and turn it into a coliseum, announcing to Bikini Bottom on a jumbotron that there will be free entertainment, promising guts and glory available to everyone in now what is called the Chum Coliseum. The coliseum is a spoof of the Roman coliseum with its battles and gladiatorial games, complete with Plankton in the Emperor's chair and a toga. Soon, the Krusty Krab is devoid of its loyal customers and Mr. Krabs and the crew go to the coliseum to find out what Plankton is up to. When they sit down, a giant lion fish is released and SpongeBob is excited until he realizes the prisoner that will be going up against the lion fish is Patrick. To entice the lion fish into chasing Patrick, Plankton orders blood sausages to be placed around Patrick's throat. SpongeBob decides to help Patrick and turns into a gladiator, complete with armor and a chariot pulled by seahorses.He soon catches up with Patrick and rescues him, but now the entertainment has turned into a chase scene that doesn't contain the blood and guts Plankton promises, even when Betsy Krabs wants to see "body parts." Meanwhile, Plankton is trying to sell chum to the crowd who are getting hungry waiting for the guts and glory. One of the spectators agrees to buy a chum stick, but is angered when Plankton tells her it will be $10. She asks why she should pay $10 when Krabby Patties are only a single buck, which Mr. Krabs agrees to. Plankton angrily tells her "You can't get entertainment like this at the Krusty Krab!" and states that the fight will be off unless she pays $10. She agrees and immediately gets sick from eating the chum stick, while the rest of the crowd, having had enough, get up to go. Plankton traps all of the customers by blocking off all the exits when they try to leave. He claims to have waited 20 years to see the amount of customers Mr. Krabs sees everyday and demands everyone to sit back down and buy his chum. They sit back down grumbling and the entertainment continues.
Going back to SpongeBob and Patrick, SpongeBob discovers that the Lion Fish is chasing the blood sausages around Patrick's neck, not them, after witnessing the Lion Fish eat a sausage that was thrown on the ground. He throws the rest of the blood sausages and they land in a pile on Plankton. He freaks out, now realizing the Lion Fish is charging towards him. He quickly escapes out of a secret door he had placed in the coliseum, taunting the Sea Lion and calling it a "prissy feline." The Lion Fish smashes through the wall and chases Plankton who runs for his life. After Plankton's failed plans, the Krusty Krab is back in business, but Mr. Krabs has raised the price of a Krabby Patty from $1 to $10. When a customer complains about it, Mr. Krabs points to the Lion Fish and tells him he can talk it up with his new "financial advisor." Mr. Krabs, SpongeBob, Patrick, and Squidward laugh altogether and then leave rather awkwardly one by one. The episode ends with the lion fish roaring.
|( ‣ ) Associated production music|
|( • ) Original music|
|( ◦ ) SpongeBob music|
‣ Roman Legion - David Farnon [title card]
‣ ? - Nicolas Carr [SpongeBob singing]
‣ Steel Licks (a) - Jeremy Wakefield [SpongeBob dialing phone]
‣ Dramatic Impact 6 - Ivor Slaney ["Mr. Krabs, you gotta get out here!"]
‣ Dramatic Impact 5 - Ivor Slaney ["It's a code blue situation!"]
‣ Zelle 503 - Gerhard Trede [Chum Bucket demolished]
‣ Keel Row - Brian Peters ["Plankton's destroying the Chum Bucket?!"]
‣ Battle March Link (d) - Keith Mansfield [Chum Bucket replaced with coliseum]
‣ Ancient Fanfare [#51] - Harry Bluestone ["Greetings, citizens of Bikini Bottom!"]
‣ Ancient Fanfare [#51.04] - Harry Bluestone ["I vow to introduce to this fair city culture!"]
‣ Ancient Fanfare [#51.05] - Harry Bluestone ["I intend to enrich your lives culturally."]
‣ Fighting Legions (b) - Gregor F. Narholz [everyone rushes in]
‣ Dramatic Impact 6 - Ivor Slaney [Plankton laughs evilly]
‣ Wooden Bear - Gil Flat, Tony Tape, Florian Voelxen ["Even though you're just a frigid machine, your circuits must be welling up with emotion."]
‣ Hawaiian Link (b) - Richard Myhill [Krabs and SpongeBob get up off the ground]
‣ Tripping Upstairs - Brian Peters ["Let's serve 'em up a burger they tell their grand-guppies about!"]
‣ Drama Link (e) - Hubert Clifford [Krusty Krab empty]
‣ Tension Bits - Nicolas Carr, Sage Guyton, Jeremy Wakefield [Krabs gets angry]
‣ Roman March - Robert Sharples ["Gentlemen, to the coliseum!"]
‣ The Tale of Ben Hur 1 - Gregor F. Narholz ["Patrick?!"]
‣ Mounting the Scaffold 1 - Gregor F. Narholz [sea lion roars at Patrick]
‣ Armed Attack 1 - Mladen Franko [sea lion chases Patrick]
‣ Entry of the Heroes (d) - Gregor F. Narholz [SpongeBob jumps into a chariot]
‣ Chariot Race - Helmuth Brandenburg [SpongeBob pulls Patrick into the chariot]
‣ Entry of the Heroes (a) - Gregor F. Narholz ["This is ridiculous!"]
‣ Plankton's Ballpark Organ - Nicolas Carr [Plankton selling chum]
‣ Steel Licks (d) - Jeremy Wakefield ["That was appalling!"]
‣ Mounting the Scaffold 1 - Gregor F. Narholz [Plankton traps everyone in the coliseum]
‣ Steel Sting - Jeremy Wakefield [they go back to their seats]
‣ Chariot Race - Helmuth Brandenburg [SpongeBob and Patrick still being chased]
‣ Vibe Sting - Nicolas Carr ["Huh?"]
‣ Chariot Race - Helmuth Brandenburg ["That's it, Patrick!"]
‣ Charge - Nicolas Carr [sausages land on Plankton]
‣ Armed Attack 1 - Mladen Franko [sea lion roars at Plankton]
‣ Grass Skirt Chase - Sage Guyton, Jeremy Wakefield [sea lion chases Plankton]
‣ The Tip Top Polka/The Cliff Polka - Chelmsford Folk Band [back at the Krusty Krab]
‣ Nude Sting - Nicolas Carr [Patrick's butt]
‣ The Tip Top Polka/The Cliff Polka - Chelmsford Folk Band [Krabs charges $10 for a Krabby Patty]
‣ Captain Lenoe's - Michael Arthur, Colin Cater, Mick Graves, The Folk Players, Sarah Graves, Simon Ritchie [everyone stops laughing]
‣ Lap Steel - Nicolas Carr [ending]
- As of August 14, 2016, The Internet Movie Database (IMDB) gives this episode a rating of 7.2/10 based on 114 ratings by users. TV.com users give this episode a rating of 5.8/10 based on 161 votes.
- The title card for this episode is similar to that of "Artist Unknown."
- The title card is a parody/reference to Ancient Greek text, but the "U" in Spongicus is not shaped like a "V" like it would have been back then.
- The episode first aired with "Nautical Novice," but was later paired up with "Suction Cup Symphony."
- On the Complete Sixth Season and Season 6 Volume 1 DVDs, this is the first episode even though it is not the first episode in season 6.
- Angry Jack can be seen in the audience of the coliseum.
- When SpongeBob gets in the chariot, his clothes transform into Roman gladiator armor.
- Like the sea bear from "The Camping Episode," the lion fish is portrayed as a fish with a predatory animal's head and claws on the tips of its pectoral fins.
- Chumsticks come in two shapes: square and corndog-shaped.
- According to this episode, the secret formula for Plankton's chum is: whale blubber, jellyfish squeezings, seahorse snout, and just a sprinkle of anchor rust. That means Plankton's chum is different from common chum.
- In a much later episode, "Jailbreak!," Plankton uses an alternate way of creating chum.
- SpongeBob is shown eagerly awaiting for a stranger to get mauled by the sea lion before he discovered it is Patrick, which is a rare time where he wants harm on someone.
- In this episode, Plankton says he has waited for 20 years to get the amount of customers Mr. Krabs sees everyday. However, in "Plankton's Army," it is the 25th anniversary of Plankton stealing the Krabby Patty secret formula. This suggests that this episode takes place five years before that one.
- On the May 13, 2015 airing, this episode was played with the audio a few seconds behind for the first few minutes. This was until the scene of the Colosseum started to fill up.
- This episode premiered on Amy Sedaris' 47th birthday, six years after "Krab Borg" and "Rock-a-Bye Bivalve" premiered, and two years after "Dunces and Dragons" premiered in Asia.
- The title "Spongicus" is a spoof of the infamous Roman gladiator Spartacus.
- The coliseum that Plankton made is similar to the Colosseum of Rome.
- The lion fish is a parody of the Neamean Lion from Greek mythology and a visual pun on real-life Lionfish.
- In the beginning of the episode, SpongeBob warns Mr. Krabs about Plankton through a pay phone in the Krusty Krab. However, the pay phone disappears in later scenes and is not seen for the rest of the episode.
- Plankton tries to boil Mr. Krabs in a giant bisque. This doesn't make sense, as "bisque" may refer to unglazed white pottery or a type of seafood soup, not a container.
- Somehow, Plankton changes his clothes and gets inside from his wrecking ball in a matter of seconds.
- Patrick's toga is white, but in one scene, it turns green.
- Plankton accepts $10 from a customer and then it disappears.
- When the people leave the Colosseum, they wind up in the area of the arena. Plankton is also in the arena when vending chumsticks. In reality, they could not go from the bleachers to the arena; corridors would lead from the bleachers to the outside of the Colosseum.
- Also, the chariot and the lion fish are not there.
- Patrick's lips turned pink, instead of black, towards the end of the episode.
- The cash register is not at the counter at the end of the episode when everyone is laughing around it.
- At the end of the episode when the lion roars and it shows the Krusty Krab, the sign is not there.