Greg Heffley
Greg is our protagonist and narrator. He's a middle schooler, although it's never specified in this book which grade he's in. Author Jeff Kinney has said in interviews that he doesn't want Greg to be a particularly sympathetic character, and indeed Greg's immaturity makes him self-centered and short-sighted. He doesn't really seem to like anybody, even his best friend Rowley.
Rowley Jefferson
Rowley is Greg's best friend and is considered immature by Greg. But Rowley finds all of Greg's jokes funny, and proves to be the more popular and talented of the two as the book goes on. Rowley is maybe the best friend Greg doesn't deserve. He briefly estranges himself from Greg after Greg lets him take the fall when Greg is mean to kindergarteners during Safety Patrol duty.
Manny Heffley
Manny is Greg's younger brother as well as the baby of the family. Greg's parents dote on Manny, and Greg gets in trouble for playing his usual pranks on his little brother. Manny earns Greg's resentment for never getting in trouble and receiving all the gifts he wants at Christmas.
Rodrick Heffley
Rodrick is Greg's older brother, and Greg's main tormenter. He's in a metal band and has marked up his old yearbook with rude remarks about his classmates. Rodrick is basically the worst version of the teen who Greg could grow up to be.
Frank Heffley
Frank is Greg's father, and he's portrayed as quick to anger and generally hapless. He's also fairly conventional when it comes to gender norms, buying Greg a weightlifting rig for Christmas and discouraging his son from playing with a Barbie doll.
Susan Heffley
Susan is Greg's supportive, if slightly overprotective, mom. She is a voice of reason in the house, letting her children pursue what they find exciting while also encouraging Greg to do the right thing. She also tends to be the one to dole out the groundings in the house.
Fregley
Fregley is the weird kid in Greg's grade. He's kind of a loner and portrayed generally as a spazz, and Greg only ends up hanging out with him to get back at Rowley for finding a new best friend. While they hang out, we learn that Fregley is over-sensitive to sugar and finds it acceptable to make Greg touch one of his boogers.
Patty Farrell
Patty is one of Greg's classmates in Geography, and tells the teacher to cover the map with all the states and capitals printed on it right before the class has to take a quiz on that exact subject. This upsets Greg, so he plots his revenge to embarrass her during the school play. Greg manages to get the other boys playing trees to throw apples at her, breaking her glasses.
Mr. Ira
Mr. Ira runs the school newspaper and leads the contest to find a new cartoonist. After Greg wins the spot, Mr. Ira changes Greg's comics to be about a dedicated student, which prompts Greg to quit the school paper.
Mr. Winsky
Mr. Winsky runs the Safety Patrol, and leads the investigation into who terrorized the children during Safety Patrol one morning. He initially accuses Rowley and makes Rowley apologize, but later finds out that Greg was the culprit. This leads to him reinstating Rowley and giving him praise as well as kicking Greg off the Safety Patrol.
