Airdate: April 13, 2007
Mr. Krabs reveals that he and Plankton were once best friends, but a fight over a formula ended it all.
Friend or Foe contains examples of:
- All of the Other Reindeer: Kid Mr. Krabs and kid Plankton were outcasts - the former is mocked for being poor and the latter for being a genius.
- An Aesop: Friends drift apart as they can get older because of differences, and that's okay. It doesn't always mean you don't like each other anymore, and it's okay to talk to them every once and a while.
- Backhanded Apology:Kid Mr. Krabs: Hey, barnacle brains, I think you owe Plankton an apology.
Classmate: You're right, Plankton, I'm sorry. Sorry you have to hang out with rag boy.
- Child Prodigy: After Patchy's attempt to make a patty fails, he tries to console himself by saying SpongeBob probably wasn't an instant success at fry-cooking either. Potty then shows a clip of SpongeBob as an infant making a perfect patty on his first attempt. Patchy is not amused with the parrot.
- Continuity Snarl: In "Enemy-In-Law", Mr. Krabs claimed the Krabby Patty recipe was a Krabs' family recipe, but here, it's shown that he developed it, by accident.
- Didn't Think This Through: Kid Mr. Krabs and Plankton try to start their own restaurant at their hangout, without success. Kid Mr. Krabs then lampshades it:Kid Mr. Krabs: Do ya think it was a good idea to open in a dump?
- Dissension Remorse: Mr. Krabs and Plankton go through this after Karen calls both of them out for letting the secret formula ruin their friendship.
- Framing Device: The episode is told in flashback by Mr. Krabs, plus a butt in from both Plankton and Karen.
- Given Name Reveal: Mama Krabs first name is Betsy.
- Go Out with a Smile: Old Man Jenkins falls unconscious this way after being poisoned by the Plabs Patty.
- Jerk with a Heart of Jerk: In the ending, it seemed that Mr. Krabs and Plankton were to restore their friendship until Plankton steals the secret formula from his pocket.
- Lethal Chef: Patchy. He keeps burger meat in an old boot, allows rats in the kitchen, doesn't wash his hands after using the lavatories and doesn't wear a hair net. Even he admits his food tastes awful after taking a bite out of his hamburger.
- Never My Fault: Kid Mr. Krabs and Plankton's partnership/friendship came to an end when they blamed each other for their first patty poisoning Old Man Jenkins.
- Pauper Patches: Mr. Krabs and his Mom were going through some rough financial times, so Mama Krabs had to fashion Mr. Krabs' clothes from rags.
- "Rashomon"-Style: Mr. Krabs claimed the moment his friendship with Plankton ended was when Plankton went mad with power. ("I'm ruling their stomachs, and soon I'll be ruling their minds!") However, Plankton appears and claimed their friendship actually ended when Mr. Krabs went mad with greed. ("First, I'll rule their stomachs, and then...their money!") But then Karen (who was just starting out as a security system at the time Mr. Krabs and Plankton started their own restaurant) shows up and revealed they didn't attract any customers at all; it didn't help that they opened their restaurant in a junkyard. In fact, the only customer they did have got poisoned by the burger. Krabs and Plankton then blame each other and fought over who gets to fix the recipe, leading them to start their own separate restaurants. Notably, all three versions of the tale involved the two tearing their original recipe in half.
- Start My Own: it's revealed that Krabs and Plankton started a restaurant together as a retaliation when the owner of another restaurant wouldn't accept them as customers. Also, before Krabs started to make Krabby Patties, Plankton broke the partnership to start his own restaurant because nobody liked the patty the two of them made together.
- Walk the Plank: After biting into the patty he had made, and finding it tastes terrible, Patchy forces it to walk the plank into the trash can.
- We Used to Be Friends: The premise of the episode.
- Wham Line: Mr Krabs reveals the shocking truth to SpongeBob.SpongeBob: Why, Mr Krabs? Why does he hate us so?Mr Krabs: Well, you might as well blame me, SpongeBob. There was a time when Plankton and I were best friends.
- Whole Episode Flashback: To Krabs' and Plankton's childhood and friendship turned rivalry.