A constant source of irritation for his older sisters, Jed never seems to take anything seriously, including his family's sharing night, a weekly tradition in which every member of the Kramer family must share a special talent in front of each other. Though Jed is sometimes lectured on his behavior, more often than not he's able to get away with his jokes.
After his sister, Amy's ventriloquist dummy, Dennis, falls apart, she is given a new one named Slappy. When Slappy arrives, odd things seem to happen. Rooms in the house are vandalized with paint, and Sara's artworks are completely destroyed. The blame falls on Jed first, as he's known for his practical jokes, but the accusations soon fall on Amy, who denies it. She tells her family that Slappy is responsible, that he's come to life, and is now committing evil acts.
However, nobody believes her. To make them see the truth, Amy and Sara enlist the help of Jed. While their parents wait in the closet, Jed will approach the dummy dressed as Dennis. He agrees, and the plan is a success. As they all watch, Jed fights off Slappy, until his head breaks on a bedpost.
Wanting to congratulate him for his effort, the Kramers approach Jed. To their shock, Jed had fallen asleep before the plan could be enacted, leaving the family to wonder just who attacked Slappy.
Jed likes to pull pranks on his family and rarely takes anything seriously. One time at family sharing night, Jed even shared a personal note Amy received from a boy at school. Despite this, Jed is still willing to help his sisters at the end of the book.
Amy describes Jed as having pale skin, curly red hair, and a freckled face, which makes him look very different from the rest of his family.