Diary of a Wimpy Kid: The Last Straw is a planned realistic fiction novel written by American author and cartoonist Jeff Kinney, the third book in the Diary of a Wimpy Kid series, and is preceded by Diary of a Wimpy Kid: Rodrick Rules. The book acts as a journal and follows the adventures of Greg Heffley, the narrator of the book. The book, according to author and illustrator Jeff Kinney, is the third of five books in the series. It will be released on January 13, 2009.
In the third book and last book based on the webcomic, Greg's father enrolls Greg into a military school, called Spag Union.
- Greg Heffley This is the main character of the entire book.He is in middle school and is the friend of Rowley Jefferson. He also likes video games and comics like most kids his age. He lies mostly to get out of problems and avoids Rodrick and older kids at his school from bullying him. He was the cartoonist of the short-lived school newspaper comic, "Creighton the Cretin", a tree in the school production of The Wizard of Oz, a safety patrol guard, and a pirate for Halloween.
- Rodrick Heffley Greg's older brother. Rodrick mainly bullies on Greg since they are in a sibling rivalry. Also, he has his own band called Löded Diper. He is fond of heavy metal and reads magazines that feature women in bikinis. He also has a liking for shrunken heads. He enjoys getting in trouble and blaming it on Greg, which almost always works. He tried to humiliate Greg by video-taping his part in The Wizard of Oz, which he failed because Greg didn't sing at all during the made-up song, We Three Trees. For Christmas he gives Greg a collection of the comic strip, Lil' Cutie, which Greg thinks is the worst comic strip ever.
- Rowley Jefferson Greg's best friend who usually helps with Greg with his schemes. Rowley is dim-witted and naive. He is an only child and also "slightly overweight." Rowley gets a lot of attention from the girls in his grade. He was falsely accused of chasing kindergarteners with a worm on a stick, which was actually Greg wearing his coat. He then told the principal and Greg lost his duty on safety patrol. He did not forgive Greg so they were not friends for a while. After that, he was the cartoonist of the school newspaper comic, "Zoo-Wee-Mama!". He was forced by bullies to eat the Cheese (a stinky piece of rotted cheese left on the school blacktop), and received the honor of being picked Class Clown in the school yearbook. Also, his mouth is almost always open.
- Manny Heffley Greg's younger brother. He calls Greg "Bubby", which he hates. Manny is also very small and has an overbite. Manny has an art for getting away with anything because he is the smallest, the "baby" and because he can use his cute looks to get out of trouble, although Frank and Susan probably wouldn't ground Manny for anything. Greg also says that Manny is an excellent climber and sneak, displayed in a scene in which Manny gets to the top of Greg's closet, picks the lock from Greg's possession box and stuffs his Walkman with brownies. Manny is fond of drawing, candy, and getting Greg into trouble. Most of the reason that he angers Greg is that he gets more rights than Greg used to have at Manny's age (three), for instance bring his "playing gear" to church so that Manny will be comfortable. In fact, from Greg's description, Manny has more rights now than Greg ever did. When Greg complains about Manny's mischief, he responds, "I'm ownwy thwee!" Also, one Christmas, Manny circled everything in a toy catalog and got everything (even though Greg warned him not to or he'd end up with all clothes). Greg said, "I bet he's glad he didn't listen to me." At a school play, Manny called Greg "BUBBY"!
- Susan Heffley Greg's mother. Susan is a middle class mom who is caring, but sometimes overcaring. Susan is a good mom and wife, but sometimes embarrasses her children/husband, but is nearly always cheery and accepting. She also likes to call Greg "Honeybunches", which usually embarrasses Greg. The fact that she never removes her glasses bears a resemblance to June Drabble, another cartoon character. Greg calls Susan "Mom" whenever he writes about her in his diary. Greg often shows evidence that Susan doesn't understand kids at Greg's age. Greg says she likes "just about every kind of music ever to exist" and dancing, even to Rodrick's heavy metal music.
- Frank Heffley Greg's father. Frank loves sports, reading and "building character." Frank hates video games, rock and roll, and his eldest son's friend Bill. Frank likes doing outdoor projects and weight lifting and many other "manly things." Frank also encourages Rodrick, Greg, and Manny to do "manly stuff" with him, especially since Greg was younger and Frank tried to encourage him to work out so he could have big muscles, only to have Greg respond with, "Muscles are GROSS!" Frank also has a habit of doing stuff for other people if they don't do things right, much to Rodrick's pleasure, especially since he "plays dumb" with his History homework. Frank also had a cat called Nutty, which his own father told him ran away to a Butterfly Farm and was very, very happy, although in reality the cat froze like a popsicle on the front porch (in winter) because Frank's dad forgot to let him in. Years later when Frank's dad came over for a family visit in the winter, he told Frank the truth, since he said he and Frank could probably laugh about it by now, but Frank threw his dad out of the house without giving him his jacket. Frank also has extremely high cholesterol but is a chocolate addict and his favorite hobby is creating his American Civil War diorama, moving around the plastic soldiers to make it as accurate as possible, painting new guns, constructing the background or the battlefield, etc. He keeps the diorama locked in a workroom in the basement and only ever let Greg get inside a couple of times when he showed him the "latest improvements". Frank never really lets anyone see the diorama, and Greg caught him telling Manny about a "monster" in the workroom to make sure that Manny stayed away from that part of the basement. Greg calls Frank "Dad" whenever he writes about him. Frank has nightmares about Rowley being a klutz and bouncing on a trampoline only to land on the diorama. Because of this, whenever Rowley visits Frank's house, he gets the same greeting by Frank: "The basement is off-limits", and Rowley says, "Yes, sir.