Spot

Spot is Plankton's pet amoeba who appears in the episodes Plankton's Pet and Spot Returns.

Plankton's Pet
Plankton once again attempts to steal the Krabby Patty secret formula and of course he fails as usual. He agrees with Karen that he should find something to get his mind off of the formula. He decides to get a pet. He goes to the Animal Shelter with SpongeBob SquarePants to find a pet. While browsing the pets, Plankton almost gets attacked by a Rock monster. As the rock is about to devour Plankton, Spot comes in and barks at the rock and bites its tongue, which is holding Plankton, and saves him. Plankton and Spot grow on each other and Plankton decides to adopt him as his pet.

Plankton wanted him to be a guard dog, but due to Spot being nice, he decides to make him a retriever. He also has the ability to grow in size and scare off any enemies who try to harm Plankton.

Spot also has the ability to eat a Krabby Patty in one bite. After he got one, he came to the Chum Bucket with it. He was offered half of Plankton's laboratory, but after eating the Krabby Patty, he got disciplined.

Spot went missing, after Plankton became upset with him. He looked all over for Spot, with SpongeBob's help. Eventually, Plankton finds Spot on his optical cornea because of the small size.

Spot Returns
In this episode, Plankton and Karen find out that Spot is pregnant with amoebas because he is in a food-rich environment caused by Plankton feeding him every day. Eventually, Spot gives birth to the amoebas, and now Plankton has to take care of them without Karen because she goes "Cute Overload" and passes out. After calling SpongeBob to help him out, they go to the supermarket where Plankton tries to get Spot's puppies adopted, but has a hard time trying to get them adopted properly.

After Mrs. Puff's puppy gets adopted, it starts to worry about Plankton and its siblings and starts wrecking the house and takes something Mrs. Puff owns.

After Plankton finds out that all the puppies did the same thing that Mrs. Puff's puppy does, he gets SpongeBob to train them to secretly steal the Krabby Patty secret formula yet again.

SpongeBob helps out with Plankton controlling the puppies, and Plankton secretly has a plan to steal the recipe. After a long hard time controlling them, and getting them to do their job of the plan on how the formula will be taken, Plankton traps SpongeBob, so the puppies can steal the formula.

After successfully getting the formula, Plankton gets distracted by Karen falling to the ground, which gives SpongeBob time to escape and retrieve the formula.

Once SpongeBob retrieves the formula, he feeds the puppies too much food and they create more puppies to become a huge puppy and take down Plankton where he stands.

Role in the Series
Spot and his puppies secretly serves as Plankton's hound when he is in the Villain League, but because Mirage is disgusted at the microscopic organisms, he quits when she tells them to leave, but they will eventually be amoeba-napped by an old rival of Plankton's from college named Sansom in his plan to create a fast food empire by stealing more formulas than just the Krabby Patty formula.