- French Narrator
- Eugene H. Krabs
- SpongeBob SquarePants
- Squidward Tentacles
- Sheldon J. Plankton
- Plankton's robot (debut)
- Karen Plankton
- Bar customers
- Plankton's imaginary family (debut)
- Plankton's cousins (debut)
At the Krusty Krab, Mr. Krabs announces to his employees that it is the 25th anniversary of the first time Plankton attempted to steal his secret recipe and explains all of his failed attempts. Suddenly, a robot enters the restaurant, and a suspicious Mr. Krabs tells SpongeBob to clean out the men's bathroom and pushes Squidward aside, saying that he will handle this customer. However, the robot orders chili coral bits instead of a Krabby Patty, while ignoring Mr. Krabs suggestions of ordering a party. The robot pays for the coral bits and leaves by blasting a hole through the doors. Mr. Krabs is left surprised that the robot was not in league with Plankton, though he is happy about the money but Plankton suddenly jumps out of the dollar bill the robot gave him. He knew Mr. Krabs wouldn't distrust money and demands for the formula. Mr. Krabs asks what happens if he refuses however, Plankton admits that he hadn't planned on what to do next, not thinking he would ever get this far. He is simply flushed down the toilet by Mr. Krabs, screaming as he gets sucked down to the sewer.
Plankton returns to the Chum Bucket, preferring not to talk about the failure to his wife. Karen shows clips of him being squished by Mr. Krabs, and more recently being flushed down the toilet, saying that he fails because he does not talk. She then suggests hiring some henchmen to help him. He first goes to a club, but the thugs smash him instead of joining him. Plankton sulks that anything he does, he just gets stepped on by people. He then realizes that he has thousands of his relatives across the sea, and invites them all to come to the Chum Bucket, thinking they will all be evil geniuses like himself. However, when they arrive, he finds out they are all rednecks, and comments that he's "been away from home longer than (he) thought."
He calls them to a meeting and introduces them to Karen, as they compliment Plankton's wife and refer to Plankton by his first name that is revealed to be Sheldon, which Karen finds hysterical and mocks his name several times. Eventually, Plankton shuts her down and tells his family of his plan, as they ask what they get for helping. After a few reveal what they want, Clem soon asks for root beer and they all get excited as Plankton promises them as much root beer that they can drink if they help, something that excites them.
It is closing time at the Krusty Krab, where a pleased Mr. Krabs tells Squidward that Plankton hasn't tried to invade all day and thinks he's learn his lesson until Plankton is heard on a megaphone demanding the formula before threatening to destroy the restaurant. Mr. Krabs and Squidward confront him and Mr. Krabs asks how he will act on his threat. Plankton shows him his family surrounding the are, something Mr. Krabs mistakes for grass until he realizes his enemy has an army. This causes him and a scared Squidward to run as the Plankton family attack the Krusty Krab, trapping Mr. Krabs and Squidward in a toilet. The Planktons open the safe containing the Krabby Patty secret recipe. Before Plankton reads the recipe, Mr. Krabs pleads him not to read it, saying "There some things this world weren't meant to be seen by mortal eyes!" Plankton tells him he doesn't care and reads it anyway. The ingredients turn out to be:
- A pinch of salt
- 3 tsp. of chopped onions
- A cup of love
- 4 lb of freshly ground Plankton
At a loss of words, Plankton looks at Mr. Krabs who says he warned him as Plankton is horrified by this, and runs away screaming from the Krusty Krab and back to the Chum Bucket. The other Planktons read it and run away (except for Clem, who can't read, but Mr. Krabs orders him to get out). Mr. Krabs and Squidward manage to escape from the toilet, and SpongeBob returns from his task and asks what happened. Squidward picks up the book and asks his boss if a Krabby Patty is actually made of plankton, Mr. Krabs explains that the recipe that Plankton read is a fake and stating that Plankton will most likely figure that out and be back to find out about the real formula.
He tells his employees that he isn't worried and states the real formula is hidden somewhere "No one, not even Plankton, would ever figure out". Squidward then correctly guesses that it's at Mr. Krabs' house under his mattress, and Mr. Krabs runs back to his house, yelling "Curse you, Squidward!"
|( ‣ ) Associated production music|
|( • ) Original music|
|( ◦ ) SpongeBob music|
‣ Keel Row - Brian Peters [opening]
‣ Premonition of Disaster - Arthur Harold Wilkinson [robot customer enters]
‣ Tomfoolery - David Snell [robot orders chili coral bits]
‣ Six Powerful Cues (a) - Wilfred William Burns [Plankton jumps out of dollar bill]
‣ Drunken Sailor (b) - Robin Jeffrey, Tim Laycock [Plankton flushed down toilet]
‣ Al Capone Blues - Eric Gemsa [Plankton goes home]
‣ Vibe Sting - Nicolas Carr ["Henchmen?"]
‣ Zelle 501 - Gerhard Trede ["I'll canvass all the seediest lowbrow dives in town to find my minions!"]
‣ Rocking Monster A - Wolfgang Killian, Hermann Langschwert [tough guys playing pool]
‣ Drowsy Reef - Sage Guyton, Jeremy Wakefield [Plankton in a wheelchair]
‣ Harp Ding - Nicolas Carr ["Wait... that's it!"]
‣ Jerry Cotton - Gerhard Trede [Plankton gathering family members]
‣ Let's Dance Susanna - Roy Henley [they're all hillbillies]
‣ Wooden Bear - Gil Flat, Tony Tape, Florian Voelxen [Plankton introduces them to Karen]
‣ Buffalo Girls - Martyn Laight ["What's in it for us?"]
‣ Zelle 503 - Gerhard Trede ["Root beer?!"]
‣ Zelle 506 - Gerhard Trede ["I have the restaurant surrounded."]
‣ Hog Fever (a) - Graham D.H. Preskett [plankton invade Krusty Krab]
‣ Kommissar X - Gerhard Trede [Krabs in toilet]
‣ The Oracle - David Farnon [safe opened]
‣ Journey to the Magic Island - Gregor F. Narholz [Plankton removes formula from bottle]
‣ Apalachian Banjo Duel - Larry Hochman ["And of course I had a little help from the family."]
‣ Dramatic Climax - Mike Sunderland [Krabs warns Plankton not to look at the formula]
‣ Against the Law (e) - Wilfred William Burns [Plankton reading the formula]
‣ Hawaiian Adventures SpongeBob Theme - Sage Guyton, Jeremy Wakefield [Plankton runs away]
‣ Let's Dance Susanna - Roy Henley ["Get outta here!"]
‣ The Tip Top Polka/The Cliff Polka - Chelmsford Folk Band [Krabs says it wasn't the real formula]
‣ Hawaiian Adventures SpongeBob Theme - Sage Guyton, Jeremy Wakefield [ending]
- This episode is available on the SpongeBob Goes Prehistoric, Absorbing Favorites, Complete 3rd Season, First 100 Episodes, and Complete Third Season DVDs.
- "Plankton's Army" was ranked #66 during the Best Day Ever event on November 9–10, 2006.
- Although this episode aired in 2004, it was made two years earlier in 2002 according to the credits.
- This episode premiered in Canada on October 29, 2004.
- The original name of the episode was "Plankton's Last Stand.".
- This was Jay Lender and Sam Henderson's final episode as writers and storyboard directors.
- This was also Sean Dempsey's final episode as an animation director.
- SpongeBob only appears in two scenes: one at the very beginning and the other at the very end. This makes the episode to be one of the smallest appearances of SpongeBob in an episode, similar to "New Leaf," "Rise and Shine," "Mall Girl Pearl,” and “Whale Watching”.
- Also, SpongeBob only has four lines in this episode.
- Plankton's past attempts at stealing the formula shown in this episode include:
- Asking nicely; Mr. Krabs says no.
- Wearing a cockroach costume; Mr. Krabs steps on him.
- Drinking a potion that turned him into a cockroach; Mr. Krabs steps on him.
- Protesting to Krabs that he is not a cockroach on a picket sign ("civil disobedience"); Krabs steps on him again.
- Plankton's line when he visits the thugs can be heard sped up in "Krusty Krab Training Video."
- This episode is one of the rare occasions where Plankton is squashed by his wife, Karen (under her robotic hand).
- In this episode, Mr. Krabs claims that Plankton has been trying to steal the formula for 25 years; however, in "Spy Buddies," he claims that Plankton has been trying to steal it for 20 years. This indicates that "Spy Buddies" took place before "Plankton's Army."
- According to the phone book:
- There are five "S. Plankton"s.
- At maximum, there is one "M. Plankton."
- There are 15 or 16 "N. Plankton"s.
- There are 15 "O. Plankton"s and "P. Plankton"s each.
- The number Plankton dialed on the phone is 1934428.
- It should be noted that when Plankton talks about how many other Planktons Mr. Krabs can handle, he says the number used in the power of ten in scientific notation. The only exception is two.
- It is revealed that Plankton's full name is "Sheldon J. Plankton."
- Despite being married to him, Karen apparently did not know Plankton's first name until this episode.
- Plankton's snare drumroll that he performed sounded exactly the same as the drumroll in episodes such as "Wet Painters" and "The Fry Cook Games."
- It turns out that Mr. Krabs hides the Krabby Patty secret formula in his mattress just like how he hides his money.
- Plankton is shown going after the Krabby Patty secret formula in future episodes, which shows Mr. Krabs was right in his predictions.
- Instead of saying he cannot read, Clem said "For what?" in Indonesia. There were also few other lines that had been edited aside that one:
- The line "You planted grass?" was changed to "You came to destroy us?" This resulting Plankton's line to respond it changed from "Grass?!?" to "Destroy?!?"
- The line "Hot dog!" was changed to "Yes! Very nice!"
- The line "I'm telling you, you won't be able to handle the truth. There are some things in this world that weren't meant for mortal eyes." changed to "I'm telling you. I mean it! There are purple print that you won't able to comprehend!"
- When Plankton had broken body parts, he appeared to have similar broken body parts to a disassembled Mr. Potatohead.
- The name of Plankton's cousin Billy Billy Bo-Illy Bonana Fanna Fo-Filly is a reference to the song "The Name Game".
- The background of the title card is camouflage, a famous pattern of clothing worn by soldiers in the army.
- When Mr. Krabs says "Today is the 25th anniversary of the first time my arch rival, Plankton, ever tried to steal me secret Krabby Patty formula," the door to Mr. Krabs' office is shown; but when the robot shows up, the door was gone, then when Mr. Krabs and Squidward walk outside, the door is back.
- When the robot shows up at the Krusty Krab, the Chum Bucket across the street is missing.
- When Plankton says "Who will join me!," his mouth is out of sync.
- When Plankton is standing on the phone book, when he says, "or 100," he is next to "S. Plankton," but when he says, "or 1000," he is next to "O. Plankton."
- The phone book does not contain phone numbers.
- Outside the Krusty Krab there are millions of Planktons surrounding the restaurant, but after Plankton retreats to the Chum Bucket, there are fewer of them.
- When SpongeBob comes back after Plankton's cousins ran away, he is not wearing his Krusty Krab Employee Hat, but in the next scene, he is.
- Karen showing "SHELDON" on her screen as Plankton is trying to talk to his relatives.
- Someone running home after they learn something horrifying, and the road is much more curved and longer than usual.
- Mr. Krabs stepping on Plankton.