It's a SpongeBob Christmas! – 9x39
Original air date: November 23, 2012
It's Christmas and SpongeBob is the happiest person in Bikini Bottom, while Squidward remains grumpy and Patrick attempts to capture Santa Claus. Plankton, however, is miserable, having committed so many naughty acts, he is on the naughty list and won't receive his Christmas wish - the Krabby Patty formula. However, he reveals to Karen his latest discovery: jerktonium, the substance that will turn anyone into a jerk, and cooks into fruitcake he intends to spread around Bikini Bottom. First, he gives the fruitcake to SpongeBob to test it, but he is resistant to the jerktonium, and upset that his plan failed, gives his fruitcake dispenser to SpongeBob, who promptly distributes the fruitcake to all of Bikini Bottom, turning all the residents into jerks, like Plankton intended. Plankton realizes that SpongeBob is so full of Christmas spirit, he is immune to jerktonium, so he sends out a Robo-SpongeBob to commit naughty deeds to defame SpongeBob. SpongeBob begins to suspect something is up when everyone acts like jerks, and goes to Sandy, who realizes what is happening, and the antidote happens to be song. SpongeBob begins singing and cures everyone from their jerktonium trance, bringing back their Christmas spirit. However, it is too late as when Santa Claus arrives, he says everyone is on the naughty list, sans Plankton, who gets the Krabby Patty formula. Santa also says that SpongeBob is the worst of all when the Robo-SpongeBob comes to kill Santa and destroy Christmas. SpongeBob fights and destroys Robo-SpongeBob with the fruitcake dispenser. Meanwhile, one of Santa's elves finds the wind-up key that proves Plankton was involved with the naughtiness, and he gets piled under coal. Santa leaves Bikini Bottom, only for Patrick to put him in a jellyfish net when Santa is flying by the moon.