Judy Blume, popular author of children's and young adult novels, wrote Tales of a Fourth Grade Nothing in 1972 as the first in a series of stories about the troublesome character Fudge. Other novels that include the character Fudge are Superfudge (1980), Fudge-a-Mania(1990), and Double Fudge (2002). Blume came up with the idea for this story after reading a newspaper account of a young boy eating a pet turtle.

The novel is divided into ten chapters, but the story is told more as separate but related episodes. Nine-year-old Peter is the narrator, and much of what he narrates is the trouble his two-year-old brother, Fudge, causes in Peter's life. For example, the story begins with Peter telling of how he won a small, green turtle at his friend Jimmy's birthday party. Peter comes home very excited because he finally has a pet. But Peter is nervous when he shows the turtle to Fudge. Although Peter tells Fudge he is never to touch the turtle, Fudge repeats Peter's command as if he understands but then breaks out into a crazy laugh. Peter suspects that Fudge is already planning some mischievous scheme.

In the next chapter, Peter's father invites the Yarby's to spend the night at their apartment. Mr. Yarby owns the Juicy-O company. Peter's father writes commercials for the sugary drink that Mr. Yarby's company makes. At first, the Yarbys think Fudge is cute, but by bedtime, the businessman and his wife have entirely different interpretations. Fudge makes a lot of noise, is obnoxious at the dinner table, and nearly ruins the Yarby's luggage by painting it. By the next morning, the Yarbys have had enough of Fudge and by way of proving it, Mr. Yarby fires Peter's father from the advertising account.

This is the general flow of Blume's novel. One catastrophe follows another as Fudge, though cute, turns the house upside down with his antics. In Chapter 3, for instance, Fudge refuses to eat for several days. His mother is frantic. She tries everything, including allowing Fudge to lick his food off his plate as if he were a dog. In Chapter 4, Fudge climbs on top of a jungle gym in the park and believing he can fly like a bird, jumps off. The fall he takes breaks his two front teeth. Peter gets in trouble for not taking better care of his brother, of course.

In Chapter 5, Fudge celebrates his third birthday with a party. He invites his friends Jennie, who bites Peter's grandmother, Sam, who is afraid of a windup toy, and Ralph, who overeats and gets sick.

In Chapter 6, Peter would like to go to the movies with his friend, Jimmy, but Peter's mom talks him into going with her and Fudge to the dentist. She suspects that she is going to need Peter to help her with Fudge, though this is not what she tells Peter. Rather, she points out that going to town together will be fun. Peter doubts it.

They first go to the dentist's office, where Dr. Brown cannot get Fudge to open his mouth. So Dr. Brown enlists Peter's help. Peter opens his mouth so Dr. Brown can count his teeth. Fudge says he can open his mouth too, but Dr. Brown tells him that he doesn't think so. Of course, both Dr. Brown and Peter are tricking Fudge, which is one certain way of getting Fudge to do what they want him to do. Next, Peter's mom takes them to the shoe store. Fudge wants to have shoes that look exactly like the ones that Peter is getting. But...