Chum is the signature ingredient of Plankton's products. As one of several major factors that causes the Chum Bucket to fail, the taste is highly considered foul in contrast to Mr. Krabs'sKrabby Patty.
During Plankton's childhood, he and his former best friend, Krabs, saw how their classmates' favorite burger joint gains "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 an argument that sparked their hostile relationship. Krabs made his own burger, the Krabby Patty, and Plankton had chum for his own. Plankton's creation proved foul even to those who can eat anything. On the other hand, Krabs's was edible. Plankton continues to use chum in most of his products. In later seasons, his chum was still inedible but another quality in his restaurant, such as the Chum Caverns or a popular slogan, would draw in customers.
According to "The Krabby Kronicle," his chum was actually chum made from real live fish, which serve as the series' characters. Chum should already be meat from fish as it is true in real life.
In the late seasons, characters gain the habit of eating chum despite tasting horrible to the customers that already ate it.
Most of the time, the chum bears a reddish-brownish color similar to that of real live beef patties.
