Jerktonium

Jerktonium is a miserable and dark substance invented by Plankton in order to ruin Christmas miracles by transforming everyone in Bikini Bottom into jerks when feeding them with fruitcake. Plankton combined Jerktonium with fruitcake, but it didn't affect SpongeBob SquarePants (because SpongeBob is immune to Jerktonium due to his big heart and 100% happiness). Plankton gave his fruitcake cart to SpongeBob, and SpongeBob accidentally feed Jerktonium-infested fruitcake to everyone in Bikini Bottom and turned them into jerks. Plankton founded out that the Jerktonium did affect everyone in Bikini Bottom. The only resistance and antidote to weaken the control of Jerktonium is a song and other happy thoughts. Only a happy person with a big heart and 100% happiness were immune to Jerktonium