The episode starts off like a normal day at the Krusty Krab. Mr. Krabs happily is doing paperwork, but becomes confused as to why his profits are down. He goes out into the restaurant to see Squidward making a sale, minus the price of a drink. After Squidward points out lack of sales on drinks, Mr. Krabs questions this. Mr. Krabs then sees everyone is drinking from bizarre-looking bottles filled with a green liquid akin to the color of seaweed, including SpongeBob. SpongeBob tells Mr. Krabs about the drink called the "Kelp Shake," which angers Mr. Krabs so much as that he bans all outside drinks from the restaurant. This, however, backfires when the customers leave without paying for their food or drinks. Mr. Krabs goes to investigate and it turns out Squidward is following the trend too.
While Mr. Krabs is uncertain if Plankton is behind these new drinks, he goes to the Chum Bucket to investigate anyway. After accusing him of creating the phenomenon, Plankton tells Mr. Krabs he has no idea what is going on because he has been relaxing the entire day. Worried the new Kelp Shakes may run the two's respective establishments out of business, they decide to work together and try to steal a Kelp Shake to discover what it is made of. They go to a Kelpshake stand and use multiple attempts, mostly involving Plankton's minuscule size to find out, but they all fail. The next day, Plankton angrily tells Mr. Krabs that he is giving up their escapade since he is the only one on the front lines. He and Mr. Krabs, who is also enraged, lament and argue over their failures, with Plankton calling Mr. Krabs a fat gorilla before SpongeBob suggests the two simply buy one, something that worries Mr. Krabs. With Plankton's motivation, Mr. Krabs reluctantly buys a Kelp Shake and goes to the Chum Bucket to analyze what is made of.
Karen starts analyzing, but Plankton gets impatient and interrupts the progress of the analyzer. They find out that the drink has two ingredients, the primary one being kelp juice. The two drink the shake and find it to be delicious, but ignore Karen, who tries warning them about the other ingredient in the drink. After going out to buy some more shakes, SpongeBob is seen running towards Mr. Krabs and Plankton, wailing and crying, as he is covered in green kelp fuzz all over his body, even growing over his clothes or outright disintegrating them. He also tells them that they are shutting down the Kelpshake Restaurants and runs away.
Then they go out and see that all Kelpshake restaurants are shut down because their shakes contained a toxic and dangerous ingredient. Then Mr. Krabs and Plankton grow the kelp fuzz all over their body. Amongst the fuss Plankton decides to go back to stealing the Krabby Patty secret formula. Instead of attempting to stop him, Mr. Krabs gives him a Krabby Patty and they chase each other around just for the fun of it.
The title is a mixture of "Best Friends" and "Enemies," making it "Frenemies."
File:The Galley Grub.jpgKelp Shakes on the Galley Grub menu in "Mermaid Man and Barnacle Boy V."
Kelp Shakes have actually appeared in the series before; the Krusty Krab has had them on stock according to the Galley Grub menu in "Mermaid Man and Barnacle Boy V."
The Kelp Shakes buildings divide like bacteria and seem contagious.
The security system which warns Mr. Krabs and Plankton says "You have three seconds before spontaneous combustion!" and then pulls out a laser, but in real life, spontaneous combustion means something that suddenly bursts into flames.
This is the second episode where Mr. Krabs and Plankton become friends. The first is "New Leaf."
This is the second appearance of a guard worm. The first is "The Lost Mattress."
This is the second appearance of the Chum Bucket analyzer. The first is "Plankton!"
The German title for this episode is "Beste Fr-einde," which translates to "Best F(r)iends."
The Greek title for this episode is "Φικοσέικ," which translates to "Kelp-Shake."
Cultural references
Kelp Shake stands are a parody of Starbucks coffee chains, which have a reputation of suddenly popping up in large numbers all over the place.
Plankton's abnormal hair growth makes him have a head-hairstyle similar to Albert Einstein. Since Plankton has an interest in science, this hairstyle that he has developed is rather suitable.
Errors
While everyone is drinking Kelp Shakes at the Krusty Krab, Harold's eyes are yellow.
When the guy who says "Wow, what a steal" orders food, he just walks away without taking any of the food he ordered.File:Born to Be Wild 08970.pngHarold with yellow eyes
When SpongeBob sucks the Kelp Shake for the first time, the straw is outside his mouth.
During the part where Mr. Krabs sneezes, an employee sign reads "Employes Only." It is missing the third "e." Also, the sign is purple, but when Plankton lands, the sign is yellow and "employee" is spelled correctly.
When the security system says "You have three seconds before spontaneous combustion!" as a warning to Mr. Krabs and Plankton, more than four seconds pass overtime before Plankton is electrocuted by a laser.
There are three Kelp Shakes next to the Krusty Krab, two on the left and one on the right, but when SpongeBob talks to Mr. Krabs and Plankton inside the restaurant, two of Kelp Shakes on the left outside are gone.
After Mr. Krabs says "Hey, get back here you little booger!," Plankton suddenly disappears out of the screen, rather than gradually disappear, like in other episodes.
Normally, Plankton's mouth is red, but in this episode, it is purple.
Running gags
Plankton getting hurt every time he and Mr. Krabs infiltrate the Kelp Shakes restaurant.
