- Eugene H. Krabs
- Sheldon J. Plankton
- Debbie Rechid
- Sandy Cheeks
- Patrick Star
- Karen Plankton
- Human crowd
- Abigail Marge
- Purple fish
- Fred (normal; blue)
- Ivy (gray)
- Harold Bill Reginald Scott
- Frankie Billy
- Squidward Tentacles
- SpongeBob SquarePants
- Nat Peterson
- Mrs. Puff
- Billy (brown fish)
- Frank (red shirt)
- Medley Fishbowl
- Sheldon (fish)
- Frank (lifeguard)
- Nancy Suzy Fish
- Nathiel Waters
- Vera Fishbowl
- Norma Rechid
- Jennifer Millie
- French Narrator
- King Neptune (mentioned)
The episode begins with another day at the Krusty Krab. Mr. Krabs once again foils another one of Plankton's attempts to steal the Krabby Patty secret formula and kicks him out. When Sandy notices Plankton and learns that he was trying to steal the formula, Plankton comments on how disappointing it is that Mr. Krabs constantly manages to thwart his efforts, despite the latter's overall lack of general intelligence. Sandy claims that Mr. Krabs would have to be as dumb as Patrick for Plankton to actually succeed in stealing the formula. This gives Plankton an idea.
Plankton breaks into Patrick's rock and takes a sample of his saliva. Plankton then makes the sauce in his kitchen, which smells horrible. Plankton explains to Karen that when he adds Patrick's saliva in the sauce, it will become Salsa Imbecilicus (aka Idiot Sauce). He plans on giving the sauce to Mr. Krabs so he will become as dumb as Patrick and get the secret formula. Karen tries helping Plankton make the sauce, since he tends to mess things up, but Plankton refuses her help. However, after Plankton adds Patrick's saliva to the sauce, it boils over and some of it splatters onto him, causing to become as dumb as Patrick. The steam from the sauce gets flown through the chimney and absorbs a nearby cloud. The cloud then rains the sauce over Bikini Bottom, which causes the whole town to become as dumb as Patrick.
The next day, Sandy notices that everyone, including her friends except Patrick (who was already dumb), are acting stupid. She learns about the accident from Karen--Karen deduces that Sandy wasn't affected because she must have been in her treedome at the time while Sandy figures that Karen wasn't affected due to the fact that she's a computer. They try snapping Plankton out of his idiocy by doing many things like shining a light on him, feeding him with nuts, and even simply yelling at him. But their efforts are to no avail. However, after Karen points out that being smart takes work, Sandy gets an idea—she and Karen start Bikini Bottom University to try and educate the entire town back into their normal selves.
By the end of the semester, Karen and Sandy have managed to educate the entire town except for Plankton, who continues to act dumb though somewhat smarter and becomes a school bully (particularly to Mr. Krabs and SpongeBob).
On the day of graduation, Mr. Krabs perfects the Krabby Patty secret formula in Home Economics, but when Plankton gets a taste of it, he tries forcing Mr. Krabs into giving him the formula. However, SpongeBob shows up to give Mr. Krabs his diploma, as neither he nor Plankton had shown up for the ceremony. It also turns out that Mr. Krabs had taken accelerated classes and actually graduated months ago—additionally, he was never actually scared of Plankton, but was just acting it out for an acting class he was taking.
Sandy gives Mr. Krabs his final grade for it (an A+) and Mr. Krabs launches Plankton outside through the window, where he smacks into Karen's computer screen. Karen takes Plankton home so he can start his "post-college years."
|( ‣ ) Associated production music|
|( • ) Original music|
|( ◦ ) SpongeBob music|
‣ The Rake Hornpipe - Robert White [Krabs kicks Plankton out of the Krusty Krab.]
‣ Fooling Around - Barry Anthony [Sandy talks to Plankton.]
• Hot Steel and Slide Licks (c) - Jeremy Wakefield [Patrick rides a skateboard on the wrong side.]
‣ Vibe Q Sting - Nicolas Carr [Plankton gets an idea.]
‣ Tales from the Swamp (a) - Ron Goodwin [Plankton laughs diabolically.]
‣ Agitation [#29] - Phil Green [Plankton in Patrick's mouth.]
‣ The Fruitcake Vendor - Nicolas Carr, Barry Anthony [Plankton making sauce.]
‣ Dramatic Bridge 7 - Phil Green ["Idiot sauce!"]
• Hot Steel and Slide Licks (e) - Jeremy Wakefield ["I think I prefer the boiling underpants."]
‣ Break In - Harry Lubin [Plankton mutes Karen.]
‣ Dark and Scary - Harry Lubin [Cloud absorbs idiot gas.]
‣ Cloak and Dagger [#70] - Phil Green [Cloud rains idiot sauce on entire town.]
‣ Gator - Steve Belfer [Sandy sees citizens acting like idiots.]
• Hot Steel and Slide Licks (u) - Jeremy Wakefield [Patrick puts a balloon in his mouth.]
‣ Gator - Steve Belfer [Krabs throwing money around.]
‣ Vibe Sting - Nicolas Carr [Sandy sees a line at the Chum Bucket.]
• Hot Steel and Slide Licks (r) - Jeremy Wakefield [A fish sucks Sandy's helmet.]
‣ Clowning Around - Barry Anthony [Karen explains to Sandy what happened.]
‣ Clowning Around Again - Nicolas Carr, Barry Anthony [Sandy and Karen trying to snap Plankton out of it.]
‣ Harp Ding - Nicolas Carr [Sandy gets an idea.]
‣ Skyline - Anthony Mawer [Karen and Sandy create Bikini Bottom University.]
‣ Lipstick and Charm - Wilfred Burns [Montage of Sandy and Karen educating everyone.]
‣ Befuddled Gent - Phil Green [Plankton writing graffiti.]
‣ Seaweed - Steve Belfer [SpongeBob stuffed in locker.]
• Hot Steel and Slide Licks (c) - Jeremy Wakefield [Patrick as a janitor.]
‣ Legion of Honor [#22] - Harry Bluestone [Graduation day.]
‣ ? - Nicolas Carr [Squidward playing clarinet.]
‣ Sneeky - Gregor Narholz [Krabs making a Krabby Patty.]
‣ Unknown Track 45 - Nicolas Carr ["Yes! That's it!"]
‣ Tipsy Turvy - Phil Green ["Something smells good!"]
‣ Dramatic Bridge 4 - Phil Green ["With this recipe, I could own the most popular fast food restaurant in Bikini Bottom!"]
‣ Pomp and Circumstance #1 (a) - John Fox [Graduates throw their caps into the air.]
‣ Hawaiian Adventures SpongeBob Theme - Sage Guyton, Jeremy Wakefield [SpongeBob goes to give to Mr. Krabs his diploma.]
‣ Danger Sign - Harry Bluestone, Emil Cadkin [Krabs about to give Plankton the formula.]
‣ Harp Ding - Nicolas Carr [Krabs gets his diploma.]
‣ Peg Leg Waltz - Michael Bolger, Nicolas Carr, Sage Guyton [Krabs says he graduated months ago.]
‣ Hot Steel and Slide Licks (x) - Jeremy Wakefield [Krabs gets an A+ in acting.]
‣ The Rake Hornpipe - Robert White [Ending.]
- This episode was originally going to be called "Idiot Sauce," but the title was changed because it was deemed that it sounded "too mean."
- Plankton could have just swabbed the saliva on the floor to get Patrick's DNA instead of going inside his mouth.
- According to Karen, Plankton has apparently boiled his underwear at least once sometime before this episode.
- Karen breaks the fourth wall by playing a laugh track after Plankton gets humiliated.
- Plankton says that a crab's brain is smaller than the point of a pencil. Actually, it is about the size of a pea.
- The clarinet song Squidward is seen playing at the graduation is also the song he performs in "SquidBob TentaclePants" and "No Hat for Pat."
- This is the first episode where Sandy and Karen work together.
- This is the first appearance of the Bikini Bottom University.
- This episode marks the first time "The Rake Hornpipe" is heard since "Plankton's Regular."
- This is the second episode where Plankton uses another character's DNA for one of his plans. The first is "Plankton's Good Eye." In that episode, Plankton uses SpongeBob's DNA, and in this episode, he uses Patrick's.
- This is the second episode where a "One-Way Chalkboard" can be seen at the end. The first is "New Student Starfish."
- There is a reference to "New Student Starfish" when Sandy observes Mr. Krabs and Plankton through a chalkboard, which is what Mrs. Puff did for SpongeBob and Patrick in the aforementioned episode.
- This episode premiered eight years after "Nature Pants," "Opposite Day," "Culture Shock," and "F.U.N." premiered in Poland and five years after "Frozen Face-Off" premiered.
- This episode premiered in Canada on David Glen Eisley's 64th birthday and one year after "Driven to Tears" premiered in Poland and "Tutor Sauce" premiered in Germany and Poland.
- In the Croatian dub, the episode's name is "Umak za idiote" which translates to "Gravy for imbeciles."
- In the Russian version, Plankton screams after Patrick's tongue licks his butt wasn't dubbed.
- Also in this version, Karen's line when she asks Plankton if he is boiling underpants was changed to socks.
- This episode takes place after "Perfect Chemistry" because Sandy and Karen first met each other in that episode.
- This episode has a similar ending to "Face Freeze!," as things do not completely go back to normal by the end of the episode.
- This episode might take place after "Patrick SmartPants," which would explain why Karen and Sandy didn't try to teach Patrick because Sandy knows what smart Patrick is like.
- The fish riding a bike on the sand in a circle is reminiscent of Curly of the Three Stooges running around on the floor.
- When Plankton goes into Home Ec, his lips are out of sync for a moment.
- When Mr. Krabs perfects the Krabby Patty recipe, the lettuce is supposed to go on top of the patty, but Mr. Krabs says it is correct.
- When Karen carries Plankton away, he disappears and reappears for a few seconds.
- Karen playing a laugh track after each humiliation.
- Patrick riding a skateboard upside down.