- Karen Plankton
- Sheldon J. Plankton
- Plankton SquarePants (debut)
- Plankton Star (debut)
- Hamster (debut)
- Incidental 107
- Incidental 103
- Squidward Tentacles
- Patrick Star
- SpongeBob SquarePants
- Incidental 48
- Incidental 7 (cameo)
- Incidental 41
- Incidental 42
- Fred (blue)
- Eugene H. Krabs
- Brain Gary (debut)
Plankton tries to steal the Krabby Patty secret formula, with Karen launching him into Mr. Krabs' brain, but ends up going into SpongeBob's brain instead. Karen and Plankton did not know SpongeBob was holding a cardboard cutout of Mr. Krabs until he moved it away.
Plankton goes into the optical system to see how to make Krabby Patties, but SpongeBob cannot see because of Plankton and uses inedible cleaning utensils as ingredients. Plankton does not realize this until he decides to go the audio system to listen to the formula, restoring SpongeBob's sight. SpongeBob is horrified at his inedible creation and thinks he forgot to make the Krabby Patty, so he asks Mr. Krabs to tell him the secret recipe again, but by the time he gets in front of him, Plankton is already using SpongeBob's eardrums. SpongeBob cannot hear Mr. Krabs, so the latter repeats himself by yelling, then by using a megaphone. This blasts Plankton away and SpongeBob regains his hearing with him and Mr. Krabs forgetting the reason for his visit.
Plankton then tries to go to the "command central", the brain, to learn about the formula. When he goes inside, he is in SpongeBob's pineapple but it is spaghetti-ish and pinkish, so he goes into the library. He looks at SpongeBob's secrets and finds that the formula is in the heart. He slides the vertebrae down there, and when he sucks information from SpongeBob's heart turns into a clone of him, from appearance to personality, while maintaining his own voice and single eye (now blue like SpongeBob's).
Karen then calls him asking him if he got the Krabby Patty recipe yet, to which Plankton knows but, now having SpongeBob's personality, refuses to share it as that would be stealing. Karen then turns his mind-reading hat into a propeller to fly Plankton out of SpongeBob and back home.
On the way home Plankton bumps into Patrick, latching onto his skull and accidentally sucking information from him, immediately transforming into a Patrick clone. Karen plucks Plankton off of Patrick while he's walking by the Chum Bucket and asks for the recipe but Plankton, now stupid as Patrick, is unable to tell her.
|( ‣ ) Associated production music|
|( • ) Original music|
|( ◦ ) SpongeBob music|
• Secret Agent 00 SquarePants - Nicolas Carr [title card]
‣ Charivari Clowns - Daniel Jean Jeannin [Plankton watching TV]
• Silly Shenanigans - Nicolas Carr, Barry Anthony ["Hey, I was watching that!"]
• Vibe Q Sting - Nicolas Carr [two people enter]
‣ Background Blues - Otto Sieben [they're visiting the most disgusting places in town]
• Steel Sting - Jeremy Wakefield [Plankton sighs]
‣ Shadow Villain - Meyer Kupferman [Karen telling Plankton how to get the formula]
‣ Danger HQ - Norman Dane ["Prepare for launch."]
‣ Armed Attack - Jean Clero [Plankton launched toward Krusty Krab/Plankton gets inside SpongeBob]
• Noodly Shenanigans - Nicolas Carr, Barry Anthony [Plankton sees what SpongeBob does]
• Jovial Pirate's Jig - Michael Bolger, Nicolas Carr ["Order number 17?"]
• Mission Improbable - Nicolas Carr, Barry Anthony ["That's it! I'm trying something else."]
• Nude Sting - Nicolas Carr [SpongeBob screams]
‣ Drama Link (g) - Hubert Clifford ["Mr. Krabs, help me, Mr. Krabs!"]
• Mission Improbable - Nicolas Carr, Barry Anthony [Plankton goes to SpongeBob's eardrum]
• Salty Krab Jig - Michael Bolger, Nicolas Carr ["Need a little refresher, eh?"]
‣ International Intrigue - Joe Sherman [Plankton unplugs SpongeBob's eardrum]
• Salty Krab Jig - Michael Bolger, Nicolas Carr [SpongeBob can't hear Mr. Krabs]
‣ Evil Mind 8 - Dick de Benedictis ["Here it comes!"]
• Salty Krab Jig - Michael Bolger, Nicolas Carr [Krabs using a megaphone]
‣ Finger of Fear - Fredric Bayco [Plankton goes to SpongeBob's brain]
• Lap Steel - Nicolas Carr ["Superficial greetings?"]
• Tension Bits - Nicolas Carr, Sage Guyton, Jeremy Wakefield ["Personal opinions? Knock-knock jokes?"]
‣ Drama Link (d) - Hubert Clifford [Plankton goes in deeper]
‣ Moon Walk - John Fox [inside SpongeBob's brain]
• What's This - Nicolas Carr ["Sounds that make Squidward upset?!"]
• Unknown Hawaiian Sting - Nicolas Carr [SpongeBob laughs]
• Steel Licks 7 - Jeremy Wakefield ["Patrick's favorite places to be scratched?!"]
‣ Zelle 501 - Gerhard Trede [the secret recipe's located in the heart]
‣ Striptease A - Peter Fallowell [Plankton's mouth watering]
‣ Straight from Hell - Gregor F. Narholz ["All of the ingredients coming together in perfect harmony!"]
‣ Drama Link (c) - Hubert Clifford ["Okay, that was weird."]
‣ Frankenstein's Niece A - Gregor F. Narholz [Plankton transforming into SpongeBob]
• Skipping to School - Sage Guyton, Jeremy Wakefield ["It's beautiful!"]
‣ Tales from the Swamp (a) - Ron Goodwin [Plankton transforming into Patrick]
• 12th Street Rag 3 with Bass - Nicolas Carr, Sage Guyton, Jeremy Wakefield [ending]
- This episode is available on the Great Patty Caper, Complete Seventh Season, Welcome Aboard, 3 DVD Value Pack Volume 2, Sunđer Bob Kockalone DVD 3, The Best 200 Episodes Ever, Kids Double Pack: Volume 4, The SpongeBob SquarePants Collection, SpongeBob SquarePants Vol. 10, The SpongeBob SquarePants 8 Season DVD Collection, and Next 100 Episodes DVDs.
- Both this episode and its sister episode, "Someone's in the Kitchen with Sandy," involve Plankton trying to steal the formula through someone else.
- This is the first episode to use "Moon Walk" since "Squidtastic Voyage."
- This is the second episode where Plankton goes inside of SpongeBob's head. The first was "Plankton!"
- However, in this episode, SpongeBob's brain is bigger than it was before.
- This was the last episode in production order to premiere during Nickelodeon's 1984-2009 Splat era.
- When SpongeBob screams as he notices the Sponge Patty he unknowingly made, his teeth are yellow for a split second.
- In this episode, SpongeBob has an eardrum, but in "Blackened Sponge," Incidental 42 says that sponges do not have eardrums.
- SpongeBob cannot hear if his eardrum is not plugged into a wire. However, when Plankton detaches his plunger from his eardrum, SpongeBob can hear again despite the fact that his eardrum is not plugged in again.
- Plankton is seen sliding down SpongeBob's spine. However, SpongeBob should not have a spine, because sponges are invertebrates. A similar mistake was made in "Roller Cowards" and "Mermaid Man vs. SpongeBob."
- SpongeBob's heart is not shown beating.
- Just as Plankton completes his transformation into SpongeBob, his eyelashes are missing for a split second.
- When Patrick walks out of the Krusty Krab, after Karen takes Plankton, Patrick's animation freezes for a second.
- Patrick's lips are pink when he leaves the Krusty Krab.
- Plankton shouldn't have consumed Patrick's personality at the end, because he only transformed into a SpongeBob clone when getting information from the heart (not the head). So the final transformation of the episode makes no sense.
- Plankton claims at the beginning to be "stuck" inside SpongeBob when he could have easily escaped out one of the holes, or had Karen fly him out towards Mr. Krab's brain.
- At the end when Karen flies him out, the cap extends to cover Plankton entirely, but once he's outside SpongeBob it isn't covering him anymore.