Manny Heffley

Manny Heffley is Greg Heffley's younger brother. Throughout the first book, he calls Greg "Bubby." In the movie, he is played by twins Connor and Owen Fielding. Manny is loosely based Patrick Kinney, Jeff Kinney's younger brother. He has also cried at least once in all of the books.

Personality
Manny Heffley is far more spoiled than Rodrick and Greg. He is extremely selfish and paranoid, never caring for his brothers at all, and panicking at anything that may harm him in any way, however minor it may be. He always gets out of trouble and gets whatever he wants in his life by showing cute and troubled looks or crying. He is also spoiled to the extreme by his mother, which always makes Greg unhappy, because he, nor his brother Rodrick, has ever gotten as many privileges as Manny. Manny isn't good at all at potty training; this is mainly because of Uncle Joe telling him to watch out for the Potty Monster, which prevented him from ever stepping into the bathroom for six months.

Appearance
Greg's illustrations depict Manny having an overbite and his teeth far apart. Manny is always depicted with a white shirt and colored shorts. Much like Greg, he has protruded hair, with three lines sticking out. Manny is about the size of a letter in Greg's journal, showing that Manny is very young.

Interests
According to the first book, Manny is a fan of the television show Sesame Street, especially the C is for Cookie sketch. Manny's interests are reasonable for his age, always asking for toys and items for little children.

Greg Heffley
Greg and Manny do not seem to get along very well, mainly due to his mother interrupting in their fun. An example could be in Rodrick Rules, where Manny laughs due to Greg pulling funny faces; their mother interrupts, telling Manny that he could be 'killed' by choking on apple juice, setting Manny off in tears and frustrating Greg. Manny always interferes in Greg's sleepovers, often forcing Rowley to leave early. In The Last Straw, Manny starts calling Greg 'Ploopy' instead of Bubby. This was because Manny's blanket got thrown away, setting him off in anger, even though Greg hadn't got anything to do with it. Greg also sets Manny off in tears for calling him Ploopy. Manny complains about the simplest of mistakes on Greg, however minor the mistake may be, and Greg always gets punished to the fullest extent by his parents.

Rodrick Heffley
Manny and Rodrick's relationship is currently unclear, but Rodrick does respect him as the person who does all the dirty work for him; he uses Manny for his fundraising and for other purposes as well.

Gramma
Manny has a somewhat unknown but curious relationship with him and his brothers' grandmother. Their grandmother mainly has pictures of Manny everywhere; the only picture depicting Greg has his head turned away from the picture. This proves that Gramma's favorite of the three is Manny; Gramma denies it, however.

Susan and Frank Heffley
Manny, overall, has an extremely good relationship with his parents, since they give a lot of pity to Manny, giving him whatever he wants in his life and providing him far more hospitality than what they would do to their other sons, Greg and Rodrick. Manny's mother, however, spoils him the most, as she is the one who will always provide Manny hospitality at any time and any place in his life. (For example, she drives all the way from work to give an extra slice to Manny's sandwich, when it was not cut in quarters.) Manny's parents also let him bring him anything he wishes to church to pass the time, which is a privilege that neither Greg or Rodrick had when they were Manny's age.

Rowley Jefferson
Although there is no existent relationship between Rowley and Manny, they do share one thing in common, which is that their parents have spoiled them. Manny has always made Rowley go home early when Rowley comes for a sleepover by causing trouble. Manny also thinks that Rowley is his role model.

Crying
Manny has cried at least once in every book.
 * Diary of a Wimpy Kid: Manny cries after accidentally swallowing a black thread, believing it was a spider.
 * Rodrick Rules: Manny cries after Susan tells Greg that he could have killed Manny by making funny faces.
 * The Last Straw: Manny cries when Rodrick melts his toys, and cries at church when Greg retaliates the joke that Manny has played on him throughout the book by calling him a 'Ploopy'.
 * Dog Days: Manny cries after being told by Rodrick that the hump is the worst seat in the car.

Trivia

 * Manny apparently hasn't been shown to have his birthday yet, but it may be shown in Book 5.
 * Manny stops calling Greg "Bubby" and "Ploopy" by the fourth book.
 * It is implied that Manny has gone potty training for about three years.
 * While explaining that the Heffley children are big quitters in the third book, Greg states that Manny "is on his third or fourth preschool by now." This implies that Manny is actually older than Greg depicts him to be, and may be as old as seven or eight.