Chum is the signature ingredient in all of Plankton's menu items.
As one of several major factors that causes the Chum Bucket to attract no customers, the taste is highly considered foul in contrast to Mr. Krabs' Krabby Patty. Although mentioned in previous episodes, chum first appears in the episode "Friend or Foe."
Most of the time, the chum bears a reddish-brownish color that has the similar color to that of real-life beef patties. According to "My Two Krabses," chum contains the organs of living beings.
During Plankton's childhood, he and his former best friend, Mr. Krabs, saw how their classmates' favorite burger joint gained "li-spect" and wealth.
Pursuing their own yet combined goals, they attempted to open their own restaurant with their own recipe and burger, which turns out to take no attention. Their burger poisoned Old Man Jenkins, resulting in an argument that sparked their hostile relationship.
Mr. Krabs made his own burger, the Krabby Patty, and Plankton used chum for his burger. Plankton's creation proved foul even to those who could eat anything. On the other hand, Mr. Krabs' tasted quite good.
Role in series
Plankton continues to use chum in most of his products, despite its foulness and overall toxicity, as shown by many having vomited after eating it. In later seasons, his chum is still inedible but another quality in his restaurant, such as the Chum Caverns or a popular slogan, such as "Chum is Fum" will draw in customers.
After Plankton complains about the fact that he has no customers, Nat Peterson comes to the Chum Bucket and orders a chumstick. He then goes back the next day and the day after that, becoming Plankton's only regular customer, and the only person who actually likes his chum. However, in the end, it is revealed that he only ordered chumsticks because Karen paid him, and he actually hates the food, so much that he already had to go to the doctor twice.
Plankton exits the Chum Bucket kitchen with "the chumstick that's finally gonna drive Krabs out of business." Andy Yellowtail, the health inspector, quickly shuts down the Chum Bucket due to one of SpongeBob's lies that Plankton uses fish in his chum.
SpongeBob learns that the cure to the Secret Patty's side-effects is actually chum. He then uses it to return everyone back to normal after they mutated into Krabby Patty zombie monsters, which helps him save the day.
Plankton's chum gets rotten during this episode, and he has to find a way to hide his chum. After hiding all of it with the help of SpongeBob through tricking him, he ends up succeeding at his goal. However, when SpongeBob tries to push down the last piece of rotten chum into a sewer, he ends up spreading all the rotten chum all over town and cause it to rain down slowly like snowflakes. This results in SpongeBob realizing it's Chum Day and make the citizens realize that too, with Bikini Bottom's kids already having the spirit of Chum Day. Despite all the happiness, a health inspector enforces the law against Plankton for chum dumping and spreading chum all over. Plankton can't pay the fine, so the inspector gives him another option: eat all the chum. Plankton does this over a long period of time, and becomes extremely big in the process.
This episode reveals Mr. Krabs' love for chum as back when he was in the navy, he tasted chum and fell in love with it. Plankton finds out about this when Mr. Krabs is searching through a trash can and the latter admits his love for chum. Plankton tricks Mr. Krabs into giving the formula by offering him a life-time supply of chum, which ends up being a hoax. Mr. Krabs tries to get the formula back but drops the formula into the chum, making Plankton swim in the chum to find the formula and Mr. Krabs eat all the chum so he could get to the formula quicker. Mr. Krabs loses his appetite for chum from eating the entire supply of chum and also ended up eating Plankton and receiving the formula in the process too.
The Chum Bucket contains a variety of products that are mostly made out of chum:
According to the episode "Jailbreak!," there is an alternate way to create chum. What is needed is:
cultural fungus growth medium (an old sock)
subtropical vegetal matter (a banana peel)
organic filler (a bucket of trash)
live bacterial culture (a recently used napkin)
After adding all of those, Plankton closes the seat and flushes it, causing them to mix together and create the chum.
In real life, chum is inedible for people, which means it is not suitable for eating.
According to "The Krabby Kronicle," his chum is actually chum made from real live fish, which serve as the series' characters. Chum should already be meat from fish, as that is how it is in real life.
The fact that chum is made of fish means the whole point of Plankton's business is to make the Bikini Bottomites engage in cannibalism. However, in real life, people use chum for bait when they catch fish.
In later seasons, some characters have gained the habit of eating chum despite tasting horrible to the customers who have already eaten it.