Friend or Foe

"There was a time when Plankton and I were....best friends."

- Mr. Krabs

"Friend or Foe" is the first episode of season 5. In this episode, Mr. Krabs tells SpongeBob and his customers the story behind his rivalry with Plankton.

Characters

 * Patchy the Pirate
 * Potty the Parrot
 * Mr. Pirateson
 * Eugene H. Krabs
 * Squidward Tentacles
 * SpongeBob SquarePants
 * Sheldon J. Plankton
 * Betsy Krabs
 * Old Man Jenkins
 * Balloon vendor
 * Stinky
 * Unnamed rat
 * Karen Plankton
 * Gorilla

Plot
A birthday cake for Mr. Krabs comes into the Krusty Krab, but when he tries to blow it, Plankton comes out and starts wreaking havoc while trying to obtain the formula. Fortunately, SpongeBob successfully stops him with help from Mr. Krabs, but not before the restaurant is a mess.

SpongeBob asks why he hates them so much, making Mr. Krabs reveal that he and Plankton used to be best friends at birth. He says his life was peaches and cream until elementary school, where Plankton was mocked for being a nerd while Mr. Krabs was mocked for being poor.

While plotting their revenge, Mr. Krabs discovers money. Later, at Stinky Burgers, everyone but Mr. Krabs and Plankton get burgers, who he sends to the back to get burgers. There, Mr. Krabs knocks on the door, only to make him mad as they could drive away his normal customers. His shift is over and he goes into his limo. After seeing how he was able to gain respect as well as tons of money by selling burgers, Mr. Krabs and Plankton start a restaurant business.

At The Dump, they start their business and make their first patty. They go to Stinky's to rub their burger in their faces, but it turns out the store is closed. Soon later, many fish come by to eat at their restaurant called the Plabs Burger, but everyone hates their food and are only eating it because Stinky's shut down.

Plankton says they are now ruling the stomachs of the children and will soon rule their brains. Mr. Krabs argues they should just be trying to satisfy the customers, causing a big argument leading to Mr. Krabs getting ejected out of their restaurant. In present day, Plankton comes and tells his own version of the story, which is the same thing as Mr. Krabs' story except their roles are reversed.

Karen comes and says both of their stories are incorrect, and that she knows the real story. The restaurant initially had no customers. The first to try was Old Man Jenkins, who ends up dying because of how awful the burger was. Mr. Krabs and Plankton accuse each other of tainting the patty and fight over the recipe, causing it to rip in half. Plankton gets the part stating “...and a pinch of chum” and storms off to pursue his own career in food.

Meanwhile, a shelf gets knocked down and several ingredients fall into the patty batter, which ends up being the Krabby Patty recipe. Back at elementary school, the two offer their food to the kids. They hate Plankton's chum, but end up adoring Mr. Krabs' chum, making Plankton vow to steal Krabs' recipe. After hearing the story, the two apologize to each other and hug it out, only for Plankton to once again steal the recipe and try to get away with it.