Simon experiments with playing positive and negative words to plants to see how it affects how they grow and thrive: the plant that hears positive words through the headphones grows happy and healthy; the plant that hears negative words through the headphones grows mean and aggressive.
Realizing that he has literally created a monster, Simon tries to capture the rogue plant, and switch out its headphones so it can listen to more positive words of encouragement in order to stop the madness.
When the boys send Dave's DNA sample to a testing lab the results show he's related to Jack The Ripper.
Jeanette and the Chipmunks try to rescue a chimpanzee Bocarter keeps in a cage.
Theodore is mistaken for an elf and whisked off to the north pole to help build toys in Santa's workshop.