Spot is a supporting character of SpongeBob SquarePants and the pet of Sheldon J. Plankton. He first appeared in the episode 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 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.