- Have a great day, sweetie pie!"
- -Susan Heffley, unknowingly embarrassing Greg
Susan Heffley (known as Ann Heffley in the online version), more commonly referred to as "Mom", is the matriarch of the Heffley family. She's the wife of Frank Heffley, and is the mother of Rodrick, Greg, and Manny Heffley. She is a member of PTA and worked as a pre-school teacher, and once was the substitute teacher in Greg's class.
Susan has a more distinct look from the rest of her family in the online and book version. Like her husband, she has an elliptical face. She wears large glasses that cover up her eyes. She has appeared in the series without glasses while sleeping. She has tall dark round hair (not used by anyone else) and she wears normal pants, either sweatpants or slim jeans, and a sweater. In The Third Wheel, a flashback photo shows she didn't need to wear glasses and had longer hair.
In the movie, Susan is played by Rachael Harris and, just like other members of her family, has brown hair and a flawless complexion. She also appears with her trademark glasses. Unlike in the book and online version, she wears make-up in the movie.
She is a rather loving and caring mother, but she constantly embarrasses Greg and Rodrick (mainly Greg) and appears to never care. Susan apparently knows very little about older children and often humiliates, embarrasses and ignores Greg and Rodrick to their dismay. Also, she showed immense favoritism towards Manny. She constantly tries to pull the family together, by getting Frank and Greg accustomed to Rodrick's band, trying to get Greg, Rodrick and Manny close to Frank, and attempting to get Greg to enjoy reading "real" literature, but none of her plans ever seem to work, and often end up in rather disastrous consequences for Greg and Rodrick. Additionally, she puts individual desires below family desires; she rarely lets anyone in the family come to a decision about an outing or purchase without her permission. According to Greg she completely spoiled Manny, giving him many privileges to Manny that she never gave to Greg and Rodrick such as bringing toys to church to keep himself entertained and buying new clothes for Manny while giving Greg's old clothes, Susan even allow Manny to verbally abused Greg by calling him Ploopy and only put a stop to it when Greg called Manny Ploopy for revenge. Susan doted Manny to the point she doesn't scold him at all even Manny commits serious mistakes and done immense mischief, this is shown to be true since even when Manny nearly got the family frozen to death by killing the lights during a blizzard, she couldn't be seeing scolding him and she once drove all the way to Manny's pre-school to cut an extra-slice on his sandwich. She also appears to give Manny a lot of money, even when he potties without being told (although this is not a big thing since he is potty-trained) and also if his brothers swear in front of him, according to Greg he even got up to $150.
- In the online book, Susan is known as Ann Heffley.
- Susan serves as the main antagonist of Dog Days.
- In the book, her glasses coving up her eyes are similar to Marcie from Peanuts.
- Susan has 4 sisters: Aunt Gretchen, Aunt Audra, Aunt Cakey and Aunt Veronica.
- Just like her mother she appears to like and favor Manny over Greg and Rodrick.
- In The Last Straw, she told Greg that Holly Hills wasn't potty-trained at 4 years old.
- Due to letting Manny have his own way a lot and letting Greg ride in a stroller, she seems to occasionally spoil her kids, though not usually.
- Similar to her second oldest son Greg, she is revealed not to get along with her siblings.
- Susan once dyed her hair blonde as revealed in a game which the family was playing in The Long Haul.
- Susan might not originally be from Greg's city since it is stated that most of her extended family comes from other states.
- She can't speak Spanish, as shown when she thinks that "what your name?" means "tè amò", which actually means, "I love you." Despite this, she tries to teach her sons Spanish.
- She seems to have a habit of using the word "real" to refer to stuff she appreciates, as though what she disapproves of is somehow not authentic. For example, she calls fast food "not real food" because she thinks it's unhealthy and she calls books that are not story books "not real literature".