Season 4 - Episode: Best Frenemies
Mr. Krabs questions why he hasn't sold a soda at the Krusty Krab. Squidward tells Krabs that they haven't sold a single soda in days. Mr. Krabs asks why not, then the camera reveals SpongeBob drinking a kelp shake, a delicious new beverage that somewhat parodies Starbucks coffee based on the way that it's a growing chain.
Mr. Krabs decides to go investigate who or what is behind the kelp shake. The camera turns back to Squidward realizing that he had one behind his back the entire time. The camera cuts back to Mr. Krabs who looks near the building. Pearl, Mr. Krabs' daughter shows up and tells him that she can't take him anywhere. Krabs keeps investigating behind the building. Turns out Plankton is on top of the building sunbathing with a drink. Krabs finds out that Plankton didn't start the Kelp Shake chain.
They continue to investigate further. They develop a series of elaborate plans to reveal what makes the kelp shake taste so good. The most notable plan being one of the first, where Mr. Krabs pulls out a jackhammer and tries to get inside. A security alarm comes out of nowhere, telling them "you have 3 seconds until spontaneous combustion". Krabs somehow escapes off-screen and Plankton gets burned.
Eventually they go back to the Krusty Krab. SpongeBob tells them, especially Mr. Krabs, "if you want a kelp shake, why don't you just buy one?" Krabs replies with "Buy one?"
The next scene shows them at the Kelp Shake restaurant. They cost approximately $5. Krabs pulls out approximately a five dollar bill and refuses to give it to the cashier at first. Plankton responds with "release your grip man, do it!"
Krabs obtains the kelp shake and then they go back to Plankton's restaurant the Chum Bucket to discover what the kelp shake is really made of. Turns out that Karen (Plankton's computer wife) tells them that the main ingredient is kelp juice, although there is another ingredient, but we never figure out what it is. Krabs and Plankton decide to take a sip of the kelp shake then drink the whole thing. Krabs says "we gotta get more".
SpongeBob runs down the street asking "What's happening to me"? The camera reveals that he has bright green fur around him. He then sobs "They've shut down the kelp shake restaurants". He continues sobbing. Krabs and Plankton simultaneously say "Huh"?
One worker tells them "I feel sorry for whoever drank this". Krabs screams with the dramatic music in the background.
The episode starts to conclude. Krabs and Plankton grow fur as well. Plankton runs to the Krusty Krab and gets the krabby patty formula only to be in Krabs' pursuit. Krabs reveals that it wasn't the formula, it was only a 10-second head start chase. Plankton says "I love being hated". Krabs' rebuttal is "Hey come back here you little booger", then laughs while Plankton disappears before the screen fades to black.