Although Greg (Zachary Gordon) is the story's protagonist and the film is told from his point of view, he's far from perfect. Greg makes lots of mistakes through the course of Diary of a Wimpy Kid as he tries to fit in and not look wimpy, not easy to do when he's pinned on the gym floor's wrestling mat by his longtime nemesis, pigtailed Patty Ferrell (Laine MacNeil). Yes, a girl! Tormented by his older brother, Rodrick (Devon Bostick), Greg is concerned about what the other kids will think of him and, of course, some of their remarks can be brutal.
He has a love-hate relationship with his best friend, Rowley Jefferson (Robert Capron of Scituate), trying to make him over into the kind of kid Greg thinks his best friend should be like. Rowley might arrive in class wearing the Mexican serape that his parents brought back from a trip south of the border. He rides a pink bike with pink plastic streamers flaring from its handlebars. Rowley has no sense that some of the things he wears or does might seem very uncool to his classmates, or that despite being Greg's age, he is not quite as socially advanced. Greg cringes when Rowley asks him in front of the other boys to come over to play after school, rather than hang out.
Both boys think they are going to become school heroes by enlisting in the Safety Patrol, only to discover that the other kids think this is the bottom of the heap on the school's pecking order. The Safety Patrol duty will figure into the film's life-changing moment, one in which Greg goes from being a nice kid to a jerk, when he places the blame for one of his own disastrously wrong decisions on Rowley and lets him hang.
While many of the things that happen in Diary of a Wimpy Kid are larger and bolder than real life a school stage set for The Wonderful Wizard of Oz looks like it was designed in Hollywood rather than banged together in shop class they all have a solid basis in the real world. These include the worries of not fitting in, of facing down bullies, of being jealous of your friends, of parents (Rachael Harris and Steve Zahn) who just don't quite understand you. Kinney understood all these things in his books and, thankfully, so do Freudenthal and Jeff and Jackie Filgo who wrote the screenplay.