It is located directly across the street from the Krusty Krab, which is far more successful than the Chum Bucket. It is part of "Sheldon Plankton Enterprises, a division of No Fun Incorporated." The Chum Bucket's lack of business is not just because of the good food served at the Krusty Krab and the most awful disgusting food at the Chum Bucket.
The Chum Bucket features a cafeteria, where food is ordered and eaten. A door in the cafeteria leads to the Lab Room, in which Plankton has his Labrador on a computer screen, though this room may no longer exist as it has not appeared since the episode "Plankton!" From here, the doors lead to the kitchen and Plankton's laboratory/living quarters. The laboratory is where Plankton does his evil experiments and builds his inventions.
In Battle for Bikini Bottom, it is suggested that the Chum Bucket may have a much larger laboratory than what is on the surface. Plankton also has an office, where he sleeps and writes his Evil Plans to steal the Krabby Patty formula from Mr. Krabs. As revealed in the later episode "Evil Spatula," Plankton has a room filled with spatulas.
The restaurant looks like a bucket with a blue hand (could be a glove) holding on to the handle of it. Double doors are placed at the front of the structure. The design of the doors are similar to the way doors in hospitals and intelligence buildings are designed. It also has a drive-thru as seen in "Komputer Overload."
Plankton opened the Chum Bucket the same day Mr. Krabs opened the Krusty Krab. It is not known why he opened his restaurant following these significant events, however, judging by his evil ways, it is presumed that Plankton wanted to rule the world and wanted to do this by stealing and selling the Krabby Patties, therefore bringing lots of people into the restaurant and ultimately ruling the world (as depicted in The SpongeBob SquarePants Movie).
It's also possible that he was jealous of Mr. Krabs and wanted to compete against him "Friend or Foe?".
Another theory was that Mr. Krabs and Plankton were once college roommates and that Krabs squished Plankton constantly but accidentally (according to a two-page comic strip titled Plankton: The College Years printed in "Nickelodeon Magazine Presents the SpongeBob SquarePants Movie").
It is estimated that Plankton thought that his future enemy was trying to kill him, and due to Krabs' greediness and advantages over Plankton (particularly when he discovered the Krabby Patty secret formula and decided to sell it), Plankton's jealousy of Krabs only grew stronger. When the Krusty Krab first came into being, the Chum Bucket was somehow built and opened by Plankton, so that he could start stealing the secret formula (which Krabs refused to give away) and soon start an ever-lasting rivalry between the two restaurants.
This may be the reason why he hates his arch-rival so much and why he constantly reminds him that "he went to college." It is unknown where Plankton had lived before his restaurant first opened.
A more plausible explanation of the simultaneous opening of both the Krusty Krab and the Chum Bucket was revealed in the episode: Friend or Foe? (originally aired April 13, 2007) where it is explained that, as school pals Krabs and Plankton were picked on by the "cool kids". Their only refuge is behind the popular local burger joint.
They must sit in back so the cool kids still want to eat there. After being shutdown Krabs and Plankton buy the empty space. Then both Krabs and Plankton tell their own versions of why they parted ways until Plankton's computer wife tells the real story. The burgers they were making were lousy and each blamed the other. They begin to fight over the recipe they have and who can improve it. The recipe rips in half sending Krabs flying into the shelf full of spices, which all fall in his patty mix.
Plankton storms out telling Krabs he would show him one day. This is how the secret recipe was born and the reasoning behind the bitter rivalry.
Imitation Krabs: After the self-destruction system is activated, Plankton screams as he wheels back to the Chum Bucket but explodes when he gets inside.
Spy Buddies: Plankton invites SpongeBob and Patrick into the Chum Bucket building, but Patrick's laser pants become so destructible that it starts carving holes everywhere and destroys the Chum Bucket. Later, the floor opens up and a blimp emerges with Plankton controlling it from the inside.
Bucket Sweet Bucket: The Chum Bucket was merely replaced with the Krusty Krab, and parts of it were used as decorations for the Krusty Krab. Even though it wasn't destroyed, it is still in the "Destruction" Category because the parts were made into something else and you couldn't get the Chum Bucket back if it was made into something else. Near the episode's end, it is proven that the Chum Bucket was indeed destroyed: the Krusty Krab is fixed up to look fancy, and the fountain was sculpted from the material of the Chum Bucket's foundation. The swords and shields on the walls were made from the walls of the Chum Bucket.
Spongicus: Plankton destroyed it with a wrecking ball and replaced with a colosseum. Later, when trying to get away from the lion, he runs outside, but the lion punches a hole through it and creates a larger hole.
Dying for Pie: It may be one of the buildings destroyed by the bomb.
Krusty Plate: It may be one of the building destroyed from the explosion of the overpowered cleaner.
'Slide Whistle Stooges': As Squidward is addicted to slide whistling he gets behind the wheel of a 18 wheeler and runs straight through the Chum Bucket and afterwards Squidward also ran into the Krusty Krab.
Move It or Lose It: Gets destroyed after the bureaucrat fish accidentally hits "Reverse" on his bulldozer.
Evil Spatula: It gets destroyed after Plankton was fooled by Mr. Krabs into mixing together a bunch of items that caused a major explosion.
In "The Krabby Kronicle," Health Inspector Yellowtail arrives at the Chum Bucket to officially close it down because of what the Krabby Kronicle says in this front page article: "Plankton's Chum Made of Your Chums!!! The Chum Bucket serves your friends in more ways than one!" Plankton and Karen are forced to watch as Inspector Yellowtail literally places the whole restaurant under lock and chains. It is later revealed that Krabs made this story up to sell his newspaper and Plankton lost the Chum Bucket in the process.
In "New Leaf," Plankton changed the Chum Bucket from a restaurant to a place that sells knick-knacks and chotchkies. He sold snow globes (one featuring a snowman, another featuring a house and pine tree), stuffed toys (including brown bears, pink bears, ducks, cows, chickens, cats, rabbits, penguins, pigs), lava lamps (in purple, green, orange, and yellow), t-shirts (black, orange, green, purple, blue, red, and pink), guitars, masks, mugs, lanterns, dolls, nets, plastic toys, and many other knick-knacks and gifts.
There have been several employees that worked for the Chum Bucket.
Plankton (proprietor) - He founded, owns, and runs the restaurant.
Karen (busgirl) - Alongside Plankton, she helps manage the establishment.
After Mr. Krabs lost a card game to Plankton in "Welcome to the Chum Bucket," he was forced to work for Plankton, who wants nothing less than a Krabby Patty. SpongeBob was annoying and troublesome and cooking up crazy food. He was later sold to the rival restaurant along with $50 after SpongeBob became too much of a nuisance for Plankton.
He was hired by Plankton five minutes before the "Fry Cook Games" after a dispute with SpongeBob. He abandoned the job at the end of the event after SpongeBob and Patrick both found out that they really cared about each other.
Most recently in "Chum Bucket Supreme," Patrick worked as an advertiser for Plankton until quitting or retiring (according to Patrick.)
Stanley S. SquarePants (presumably fry cook) - Mr. Krabs sent him to work there because he breaks everything he touches in "Stanley S. SquarePants". Plankton, at first, thinks he is just as good as SpongeBob, but he winds up destroying the Chum Bucket.
Patrick Robot (invention) - On SpongeBob 4-D, Plankton creates a Patrick robot that steals a pickle from the Krusty Krab in order to get the recipe. However, the robot gets unplugged by the real Patrick.
Cave Dwellers - In the episode Chum Caverns, the Cave Dwellers were hired by Plankton to sell his chum in the beautiful caverns. One of them eventually worked for the Krusty Krab at the end of the episode.
The Chum Bucket usually barely has any customers due to Plankton's disgusting food and because the Krusty Krab is much better than his failing restaurant. It is unknown how Plankton keeps his restaurant open, which is also his residence with his computer wife, Karen. There is also no explanation as to how Plankton can fund his evil schemes, since the Chum Bucket is unprofitable.
In the beginning of the episode "Enemy In-Law", a giant Plankton-shaped robot named Chum-Bot kidnaps citizens of Bikini Bottom and deposits them into the Chum Bucket so that Plankton can sell them his food.
In the episode New Leaf, Plankton says that the only customer was a rat that died when it ate Plankton's food even though rats can't survive underwater since it would be impossible for a land animal (the rat) to survive underwater.
However, The SpongeBob SquarePants Movie was the only time that the Chum Bucket was highly popular. A series of incidents planned and caused by Plankton led to the near-execution of Mr. Krabs by King Neptune. This left Plankton to steal the Krabby Patty secret formula and sell Krabby Patties, therefore filling the void left by the Krusty Krab. Plankton even sold bucket helmets, only to turn the wearers into his robot slaves as soon as Squidward Tentacles threatened to expose his evil plans. It is not known what happened to his restaurant after he was arrested.
Plankton also lured customers in by hypnotizing Mermaid Man and Barnacle Boy and making them say they prefer the Chum Bucket in front of the Krusty Krab clientèle in "Mermaid Man vs. SpongeBob." In this episode, Plankton claims this is the first time he's had to serve food in the Chum Bucket to customers.
In the episode, "Plankton's Regular," it seemed as if Plankton had a "regular" customer (Nat Peterson) who actually liked his Chum on a Stick. However, it was later revealed that Karen paid him to eat the chum, and he stops by giving her back the cash and being carried out of the Chum Bucket to get his stomach pumped.
In the episode, "Chum Caverns," Plankton opened an underground restaurant which was also highly popular. The scheme operated on the fact that the customers were so taken by the scenery that they paid no mind to the food.
In the episode, "Your Shoe's Untied," a customer shouts that they will eat at the Chum Bucket. Whether they really did or not is unknown.
In the episode, "Chum Fricassee" Squidward quits his job at the Krusty Krab and goes to work for plankton. He then uses his grandmother's recipe to make chum taste good which nearly causes Mr. Krabs to go out of business. Though this could count as karmic punishment due to Krab's poor treatment of his workers.
Plankton has various ways to advertise the Chum Bucket. Like the Krusty Krab, there are many billboards advertising the Chum Bucket on Sand Mountain. Plankton has a telephone directory ad in the Bikini Bottom Yellow Pages. See episode "Enemy In-Law". The restaurant's slogan is Eat or Die! He paid a lot of money for that ad. In SpongeBob's Last Stand there's a billboard that's says the Chum Bucket's past logo Chum is Fum. Also in Gary's New Toy there's a bench with the Plankton on the Chum Bucket's phone number. The Chum Bucket's phone number is 1-800-EAT-CHUM. The bench is by the bus stop.
When Karen suggested advertisement, Plankton had "came up" with the idea and made a sign on his restaurant that read "CHUM IS METABOLIC FUEL". It gained no attention from any customers but customers came once Patrick made a change to Chum is Fum. When the success started with a batch of customers, Plankton hired Patrick to create slogans and was Plankton's entire "marketing department". Later on, the second slogan was so successful that the billboards began to advertise the Chum Bucket. One day customers got tired of saying 'Chum is Fum'. Plankton tells Patrick the Chum Bucket needs a new slogan. After three days Patrick thinks of the slogan 'Fum is Chum' which customers also liked. Then, Patrick resigned and an angered Plankton started revealing his true hatred on his customers which made him lose his customers, thus undoing what his slogans created. Strangely, one billboard with the slogan was present at "SpongeBob's Last Stand."
All of the food served at the Chum Bucket begins with the word "Chum" (with the exception of Raspberry Tea, Bran Muffin, and Prune Danish), where the name of the restaurant comes from. Only after King Neptune accused and froze Mr. Krabs for stealing his crown when it was really Plankton's fault, did he start selling the delicious Krabby Patties here... but only briefly. Plankton has absolutely no talent in cooking whatsoever, with whatever he cooks being foul tasting at best and coming to life at worst (in two episodes however, Plankton succeeds in getting customers, in which eat the chum on their own). Of course, Plankton is completely oblivious to this and considers whatever he makes to be good, such as calling a dish that melted the cooking pot and the floor "delectable". It is revealed in the episode "Spongicus" that Plankton's chum is made out of jellyfish squeezings, whale blubber, seahorse snout, and a sprinkle of anchor rust. Also, under the large version of the menu in the cafeteria is a sign that says, "WARNING." In the episode "Chum Bucket Supreme," it is revealed that the Chum is so foul that even Plankton himself won't eat it (he fakes eating it by making a chewing motion while moving the Chum behind his head, thus, giving the poor illusion it is shrinking as he eats it, and Karen is ridiculed.) In "Free Samples", it is revealed that Patrick Star is the only one who can eat chum compare to anyone else who eats it. And in "Chum Caverns," Patrick ate a lot of Plankton's Chum which means he is the only one who loves eating chum, though he doesn't know his chum is located in the Chum Bucket.
Chumburger - the chum burger was invented by Plankton after he split away from Mr. Krabs. This was the very first item. The first customer to try it was one of Plankton's classmates, Johnny.
The Analyzer: An hour-glass shaped device that will determine the composition of an object placed inside it and show the results on Karen's screen. It was seen in Plankton!, where it analyzed seaweed (50% Sea, 50% Weed) and Plankton (1% evil, 99% hot gas). It also made an appearance in One Coarse Meal but was renamed the "TransMutator".
Plankton Robot: A giant robot used to steal Mama Krabs and also snatch people and place them in the Robot.
Robot Krabs: A Mr. Krabs-shaped robot built by Plankton in Imitation Krabs to obtain the Krabby Patty formula. It was subsequently destroyed due to its coin-operated self-destruct feature. It was also seen briefly in New Leaf and Spy Buddies
Switch Lives Just to Know What It's Like-O-Mogrifier: An invention that will let Plankton switch with a dolphin, mermaid, jellyfish or a crab as seen in the episode: The Algae's Always Greener.
Sandy Robot Exoskeleton: A crude robot made by Plankton in Someone's In The Kitchen With Sandy. It was made using Sandy's stolen fur pelt as it's skin. Plankton attempted to use it to steal the Krabby Patty recipe, but was stopped by a furious, hairless Sandy, who then took back her fur pelt. Its fate remains unknown.
Eye Scanner: Briefly mentioned in a Nick Magazine comic, this security scans all visitors to see if they are one-eyed, like Plankton. It has not appeared since.
Plankton's Death Robot: A robot that was seen in Eek, An Urchin!. Plankton used this robot to try and destroy the sea urchin but ends up wrecking the Krusty Krab instead. The Death Robot was destroyed by Mr. Krabs after it attempted to destroy his cash register.
Majestic Sizzlemaster: A special type of spatula that was seen in the episode Evil Spatula. Plankton used this spatula to try and get the secret formula out of SpongeBob. The plan was foiled by Mr. Krabs, however.
In the Brazilian dubbing of the series, Chum Bucket has two names: "Balde Camarada" (Chum Bucket) and "Balde de Lixo" (Garbage Bucket). However, the name Balde de Lixo is used in almost the whole series, while Balde Camarada is heard a few times.
The Chum Bucket is the worst restaurant in Bikini Bottom.
In the Lego SpongeBob Series, the Chum Bucket will be released soon including SpongeBob, Plankton and Robot SpongeBob.
In "Free Samples," it is revealed that Patrick Star is the only one who can eat chum compared to anyone else who eats it. And in Chum Caverns, Patrick ate a lot of Plankton's Chum which means he is the only one who loves eating chum, though he doesn't know his chum is located in the Chum Bucket.