Jerktonium is a toxic chemical-filled element that is known to change the Bikini Bottomites into jerks (except SpongeBob, due to his pure heart and small brain). They also have big black bushy eyebrows, black baggy eyes and five o'clock shadow.
Plankton discovered the material and planned to use it on people in Bikini Bottom to make himself look good compared to them. His first victim to use it against was SpongeBob. He made SpongeBob try the Jerktonium-laced fruitcake but it didn't work on him making Plankton angrily gift the Jerkmaker-9000 to SpongeBob. Shortly after that, SpongeBob (unknowingly) gives fruitcakes contaminated with Jerktonium to everybody in Bikini Bottom after obtaining the Jerkmaker-9000 from Plankton.
Seeing that the Jerktonium worked on other people in Bikini Bottom except SpongeBob, Plankton constructed a robot known as "ToyBob" to wreak havoc in Bikini Bottom which ruined SpongeBob's reputation.
Later SpongeBob realizes that people in Bikini Bottom were acting like jerks so he decided to ask Sandy for help. After getting help, SpongeBob sings the song "Don't be a Jerk (It's Christmas)" to cure everyone; they join in. When Santa arrived around at the Krusty Krab, he prepares to give everyone (except Plankton) coal and gives Plankton the Secret Formula from Mr. Krabs. Shortly after, ToyBob, arrives to wreak havoc, but SpongeBob defeats him with the Jerkmaker-9000 in time to save Bikini Bottom. This caused Plankton's plan to get the Secret Formula to fail due to Santa identifying, from ToyBob's remains, that the robot actually belonged to Plankton himself. After that, Plankton is put back in the Naughty list, and everyone gets a present while Plankton surrenders the formula and gets a bag of coal tipped over his head.