Greg Heffley begins the Diary of a Wimpy Kid by stipulating that it is definitely not a “diary,” because he is afraid that other kids would make fun of him if they knew he was writing about his feelings.
At the beginning of the new school year, Greg laments that “this whole popularity” thing has become so much more complicated, now that he’s in middle school. Greg knows that he is only “around 52nd or 53rd” most popular in his school, but he wants to move up in the school hierarchy. At the moment, however, Greg’s best (and only) friend is Rowley, who doesn’t care what people think of him. In the first few months of school, Greg engages in various schemes to try to become more popular and raise his social status. He runs for treasurer in student government, but loses, as his campaign centered exclusively on making fun of his opponent. He tries to open a haunted house in Rowley’s basement, but gets in trouble with Rowley’s dad. He is horrified to be partnered with the “weird kid” Fregley in physical education class—the only boy lightweight enough to wrestle with Greg—but his attempts to build muscle by weightlifting don’t go as planned because he hates exercise.
There are other problems in Greg’s life too. He lives in terror of “the Cheese,” a moldy bit of cheese left out on the basketball court that will condemn anyone who touches it to the “Cheese Touch” and a life of social ostracization. He is frequently bullied by older and more physically intimidating kids, like the teenagers who spray him and Rowley with water on Halloween. Greg loves playing video games, but his dad is always telling him to go outside and enjoy the sunshine or punishing him by taking away his video gaming time. And perhaps worst of all, Greg’s mom makes him audition for the school play. Greg is cast as a tree in The Wizard of Oz, but he manages to sabotage and shut down the entire performance after he pelts the lead actress with apples, breaking her glasses.
At Christmas, Greg is dissatisfied with his gifts and jealous of his younger brother, Manny, who he thinks gets an unfair amount of attention from their parents. In his ongoing quest to gain a position of authority in the middle school social hierarchy, Greg and Rowley volunteer for the Safety Patrol, a group of students who walk the kindergarteners home from school. Greg also makes a bid for the role of the school newspaper cartoonist and gets the job—but this backfires when the math teacher in charge of the newspaper, Mr. Ira, re-writes Greg’s comic strip so that it contains a message about how to properly add fractions.
Meanwhile, Rowley gets in trouble for reportedly “terrorizing” the kindergarteners during Safety Patrol, although it was actually Greg who terrified the children with a worm—he was misrecognized by a neighbor because he was wearing Rowley’s hat. Greg lets Rowley take the blame, so Rowley stops speaking to him and instead begins having sleepovers and hanging out with another friend, Collin Lee. Greg tries to get back at Rowley by hanging out with Fregley, but admits that he misses Rowley. To make matters worse, Rowley suddenly becomes popular. He breaks his hand and has to wear a cast, which garners sympathy from girls. He also writes a comic strip called “Zoo-Wee-Mama,” that all the students and teachers seem to find hilarious. This makes Greg jealous, since he had hoped to be elected “Class Clown” in the school yearbook, and “Zoo-Wee-Mama” was originally his idea.
The conflict between Greg and Rowley comes to an end, however, when both are bullied by the same teenagers who chased them on Halloween. To get back at Greg and Rowley for running away that night, one of the teenagers drags Rowley over to the Cheese and makes him eat it. The next day, all the students wonder where the Cheese went, and Greg knows it’s only a matter of time before someone figures out that he and Rowley were involved. If people found out that Rowley ate the Cheese, Greg knows that they would bully and ostracize him. To protect Rowley, Greg tells everyone that he was the one who threw away the Cheese—meaning that it is Greg, not Rowley, who now supposedly has the “Cheese Touch.” Greg and Rowley become friends again, and Rowley is voted “Class Clown” in the yearbook. Greg decides that he’ll only tell people about what really happened to The Cheese if Rowley gets a big head about being the class clown.