"The World’s Worst Babysitter" is a story narrated by Bret Ernst in the stand-up comedy show "This Is Not Happening." Bret shares his experience of being the worst babysitter in the world while taking care of his nephew, Jake. He recounts how he ignored Jake's needs, fed him junk food, exposed him to age-inappropriate movies, and let him play with dangerous objects. Despite being a terrible babysitter, Bret realizes the importance of learning from his mistakes and becoming a better uncle.