- Sheldon J. Plankton
- Karen Plankton
- Spot's Children (debut)
- SpongeBob SquarePants
- Elephant Bubble (cameo)
- Caterpillar Bubble (cameo)
- Eugene H. Krabs
- Patrick Star
- Gil Scouts (debut)
- Barg'N-Mart Customer (debut)
- Mrs. Puff
- Other Amoeba Owners (debut)
- Mrs. Puff's Snail (cameo in picture)
- Popeye Fish
- Frankie Billy
- Con Man
- Casting Director
- Squidward Tentacles (cameo)
- Spot's Grandchildren
The episode starts at the Chum Bucket, where Plankton is searching for Spot. He finally finds a fat Spot and gives him a snack. Then, Karen comes to check Spot out, as she is wondering if Plankton is giving him too many treats. Plankton continues treating him well and Spot belches in front of him. Wanting to prove that the latter is still healthy, Plankton shows Karen its insides with X-rays, only to see that Spot is pregnant. Karen explains to him that food-rich environments such as the one Plankton provided to Spot causes amoebas to reproduce. Plankton starts panicking, while Spot is generating other amoebas. Plankton is happy that Spot made it out fine and Karen starts smearing the new amoebas on her screen. However, she gets overloaded from so much cuteness, resulting in her getting damaged. While she is rebooting, Plankton tries to control them. The amoebas destroy various things in the lab, leading Plankton to attempt to get rid of them, as they can't hear him.
A happy SpongeBob is walking down the street, making bubbles in the form of an elephant and a caterpillar. When he sees a sign near the Chum Bucket that reads, "FREE AMOEBA PUPPY WITH ORDER OF CHUM," SpongeBob says hello to Plankton so he can see what's going on and Plankton tells him that he wants to sell Spot's puppies. SpongeBob offers Plankton to let him help have the puppies adopted.
At Barg'N-Mart, Plankton drives off two scouts and their bench with their biscuits so he and SpongeBob can make room for their business. SpongeBob suggests that Plankton start acting politely, but the latter doesn't seem to want to do so, evidenced by him making two of the Barg'N-Mart customers run away as fast as they can. Then, SpongeBob takes some of the amoebas, only to make a big puppy. Dave notices it and wants the puppy, so SpongeBob gives him one. A crowd of people are waiting to buy one, including Mrs. Puff, who remarks with how cute those amoebas are. SpongeBob makes, with the help of his body, more of them. However, things don't go quite positive, as an amoeba who is alone at Mrs. Puff's House starts destroying everything in their way, showing the consequences of leaving one alone.
Mrs. Puff's puppy comes to the Chum Bucket. Plankton sees that it has swallowed a pearl necklace from Mrs.Puff, which makes him call him a bad puppy. It is not late for him to notice that all the other puppies came back, each of whom having something from their owner swallowed. Plankton takes from the puppies all those things, as a theft. That of the Krabby Patty secret formula is now on his mind. He is about to start training them, but Karen is still rebooting, and Plankton finds it difficult to do that alone.
Plankton calls SpongeBob to train his pets. As soon as the training starts, SpongeBob shows them how to do innocent things, such as sitting and barking, while Plankton is shown at one of them how to do other things for evil purposes, such as opening a door and catching a grenade. After hours of training, Plankton introduces SpongeBob to the puppies: the Demolition Puppy, the Acrobat Puppy, the Identical Twin Puppies, and the Comic Relief Puppy. SpongeBob realizes that this has to do with the theft of the Secret Formula, and Plankton traps him inside a cage, while explaining the plan he has in mind:
- Distraction with the Identical Twin Puppies inside the Krusty Krab.
- The Acrobat Puppy goes inside Mr. Krabs' office and opens the window.
- The Demolition Puppy goes inside Mr. Krabs' office from the window and opens with explosives into the safe, so it can take the formula.
- The Comic Relief Puppy ends with a dollop of humor.
SpongeBob, although he doubts that this plan will work, doesn't know that this is actually what the puppies were doing all that time. While Plankton tries to open the bottle with the Secret Formula that the puppies gave to him after succeeding with the plan, SpongeBob throws with his tongue one of his eyes to Karen, which makes her fall down. Plankton goes to see what happened to Karen, and SpongeBob takes again the shape and form of an amoeba, whistles at the puppies and starts barking, so the puppies can do one of the tricks he learned to them during the training. The puppies end up freeing SpongeBob from the cage with switching a lever, and he takes away the formula from Plankton, who just raised Karen. SpongeBob decides to throw at him some treats, so the puppies can eat them and become bigger. The final size of them makes Plankton's restaurant blow up, with the formula rolling to Patrick, who is Mr. Krabs' pet in this episode. He gives the formula he found back to Mr. Krabs, who rewards him with a treat. Karen is now fully rebooted and looks at the amoebas on the floor of the restaurant as adorable again. She makes a maze of them, which results in a bigger amoeba, and the episode ends with it falling onto Plankton.
|( ‣ ) Associated production music|
|( • ) Original music|
|( ◦ ) SpongeBob music|
‣ Whistling Around - Nicolas Carr, Sage Guyton, Jeremy Wakefield [Title card.]
‣ Tomfoolery - David Snell [Opening.]
‣ Hot Steel and Slide Licks (d) - Jeremy Wakefield ["All right, Doctor. If you say so."]
‣ Unknown Track 72 - X-ray of Spot.
‣ Wooden Bear - Tony Tape, Gil Flat, Florian Voelxen [Plankton finds out that Spot is pregnant.]
‣ Happy Links 1-5 - Paul Fenoulhet [Spot reproduces/Spot licks Plankton/Karen rubs the slime all over her screen.]
‣ Hot Steel and Slide Licks (m) - Jeremy Wakefield ["You take a couple of hours to reboot, Karen."]
‣ Fresh as a Daisy - George French [Puppies eating everything.]
‣ Cartoon Sting 8 - Barry Anthony [Plankton wants to get rid of the puppies.]
‣ Hello Blues - Sage Guyton, Jeremy Wakefield [SpongeBob blowing bubbles.]
‣ Vibe Sting - Nicolas Carr ["Free amoeba puppies?"]
‣ The Fruitcake Vendor - Nicolas Carr, Barry Anthony [SpongeBob offers to help Plankton get the puppies adopted.]
‣ Lap Steel - Nicolas Carr [Patrick lifts his leg.]
‣ Tom Fool - Van Phillips [SpongeBob and Plankton giving away puppies at Barg'N-Mart.]
‣ Dramatic Cue (c) - Ronald Hanmer [Mrs. Puff's puppy destroys her house.]
‣ Careless March - Marc Dall'Anese [Mrs. Puff's puppy runs back to Plankton.]
‣ Vibe Q Sting - Nicolas Carr ["Puppy? You came back?"]
‣ Careless March - Marc Dall'Anese [All of the puppies get back to Plankton.]
‣ Drama Link (c) - Hubert Clifford ["...But perhaps there is something you could get for me..."]
‣ Drama Link - Georges Van Parys ["...like the Krabby Patty secret formula?"]
‣ Hot Steel and Slide Licks (e) - Jeremy Wakefield [Plankton coughs.]
‣ Prelude to Conflict - Sam Fonteyn ["Come on, pups! We've got some training to..."]
‣ Horror-Scope - Ronald Hanmer [Karen's still rebooting.]
‣ Skipping to School - Sage Guyton, Jeremy Wakefield ["I'm glad you called me, Plankton. I am the best pet trainer in all of Bikini Bottom."]
‣ Whistling Around - Nicolas Carr, Sage Guyton, Jeremy Wakefield [SpongeBob and Plankton training the puppies.]
‣ World in Action - Laurie Johnson [Plankton introduces the puppies.]
‣ Eight Dramatic Bridges - Ronald Hanmer ["Of course it is, and there's nothing you can do about it!"/Plankton puts SpongeBob in a cage.]
‣ Persuasion - Johnny Hawksworth [Plankton explaining his plan to SpongeBob.]
‣ Acrobats and Clowns (a) - Alfi Kabiljo [Comic relief puppy is shown.]
‣ Lap Steel - Nicolas Carr ["That's never gonna work!"]
‣ The Escape - John Scott [Puppies appear with the secret formula.]
‣ Hawaiian Adventures SpongeBob Theme - Sage Guyton, Jeremy Wakefield [SpongeBob distracts Plankton and takes the secret formula.]
‣ Hot Steel and Slide Licks (h) - Jeremy Wakefield ["Come on, SpongeBob, maybe we could work something out!"]
‣ Grass Skirt Chase - Sage Guyton, Jeremy Wakefield ["Sorry, Plankton. You leave me no choice."]
‣ Shellfish Behavior - Sage Guyton, Jeremy Wakefield [Ending.]
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- As of December 8, 2017, The Internet Movie Database (IMDB) gives this episode a rating of 9.5/10 based on 140 ratings by users. TV.com users give this episode a 9.3/10 based on 3 votes.
- This is Spot's first appearance since his debut in "Plankton's Pet."
- When Karen names some of Spot's puppies, one of the names she chooses is "Vincent," referencing Vincent Waller, one of the show's crew members.
- The photos in Mrs. Puff's house show Mr. Krabs (her boyfriend) and her pet snail.
- This is the third episode to contain the word "returns" at the end of the title, the first being "Squilliam Returns," the second being "Bubble Buddy Returns," and the fourth being "Man Ray Returns."
- This episode was leaked on a website two days before its premiere, along with "The Check-Up". Just about 15 minutes after leaked, they're removed from that website. 
- This episode possibly takes place after "Mimic Madness" because SpongeBob is able to control his Mocking Mimicry Madness when acting as Spot.
- This episode possibly takes place after "Don't Wake Patrick" because SpongeBob nearly throws up on account of swallowing a pot of chum by accident.
- When SpongeBob is blowing bubbles, he makes an elephant bubble and a caterpillar bubble in reference to "Bubblestand."
- This is the second episode where the children of the character returning have a bigger role than said character returning. The first was "Bubble Buddy Returns."
- This is the third time Patrick behaves like a pet, the first being "Grooming Gary" and the second being "Treats!"
- This is one of the few episodes where Squidward appears but has no lines.
- The scene where the puppies are introduced could be a reference to "Komputer Overload" when the robots in that episode are introduced.
- Strangely enough, there's an overload problem Karen experiences that causes her to reboot in this episode.
- This episode premiered four years after the premiere of "Little Yellow Book" and "Bumper to Bumper" in Greece, three years after the premiere of "Krusty Towers" and "Mrs. Puff, You're Fired" in Poland, two years after "The Adventures of SpongeBob SquarePants" was released in Australia, and one year after the premiere of "SpongeBob LongPants" and "Larry's Gym" in Canada and "Patrick! The Game" premiered in Poland.
- Karen's rebooting sound effect sounds like one of the old Macintosh sound effects.
- Demolitions puppy bears a strong resemblance to the demoman from Team Fortress 2, sharing a similar design.
- The gag flower worn by comical puppy is similar to Luan Loud's flower from The Loud House.
- Spectrum and DirecTV list this episode as season 10, episode 10. Its sister episode, "The Check-Up," shares this trait.