Plankton's 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.
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.
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.
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 (which is nationally illegal). 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.