Nikki J. Maxwell is the main character of the series and a new student at Westchester Country Day. Because Nikki feels completely out of place among all of the wealthy, designer-clad students, she spends most of her time alone writing in her diary. Nikki has short brown hair, often in pigtails, and green eyes. She depises her locker neighbor (and enemy), MacKenzie Hollister. Nikki claims that she's the most unpopular girl at her school (only slightly above the gym shower slime). Nikki only attends WCD because her dad arranged a scholarship as part of his contract as the school's bug exterminator. She has a crush on Brandon Roberts. Her art skills are well above average (despite her going to art camp every summer) and won WCD's art competition with the help of her friends in the first book. She is, however, extremely bad at math. Nikki has a 6-year-old sister named Brianna. She is best friends with Chloe and Zoey and works with them in the Library. When she grows up, she wants to be an artist. She was selected as the chairperson for the Halloween Dance after MacKenzie Hollister decided to not be the chairperson and saved the dance. Her relationship with Brandon grows in the 3rd book of the series.
MacKenzie Hollister is the "most popular girl" at Westchester Country Day and the leader of a clique known as "Cute, Cool & Popular" (CCP for short). Her locker is next to Nikki’s. MacKenzie is wealthy, self-centered, always wears designer clothes and large amounts of lip gloss and carries expensive handbags. She, too, has a crush on Brandon Roberts and tries to flirt with him by twirling her hair whenever possible, not knowing that in fact Brandon does not feel for her. MacKenzie does not like Nikki and calls her a dork. She talks behind Nikki's back and tries to "wreck her social life" with the help of her best friend, Jessica. Like most popular girls in stories, she has blonde hair and blue eyes. MacKenzie has an "annoying" little sister named Amanda. She entered the avant-garde art competition, but lost to Nikki. She revealed in the first book that she has a dog.
Chloe Christina Garcia is Nikki’s best friend. Chloe is Hispanic, works in the library with Nikki and Zoey and is an avid reader, particularly young adult romances. As a result, she is an expert on "guys and dating," according to Nikki. Her parents own a software company. She is described as being the "5th most unpopular girl" at Westchester Country Day.She(according to Nikki) read almost every single teen magazine and romance novel there ever is.
Zoeysha "Zoey" Ebony Franklin is Nikki's other best friend, a "bookworm who likes self-help books and editing Wikipedia". Zoey also works in the school library with Nikki and Chloe. Her mother is a lawyer and her father is a record executive, although they are divorced. Zoey is billed as "the 7th most unpopular girl in the school" in the series.She is described to be a human wikipedia by Nikki.
Brandon Roberts is Nikki's love interest. Although Brandon is also MacKenzie's love interest, he is shown to like Nikki more throughout the series. He is the school's photographer and reporter for the school newspaper. He also plays the drums. Brandon is shy and sweet towards Nikki and her friends. He has brown hair and blue eyes.Brianna Maxwell is Nikki’s 6-year-old sister. Brianna is afraid of the tooth fairy because Nikki told her that the tooth fairy collects children's teeth to make dentures. She has an friend named Miss Penelope (which is a face she drew on her hand). According to Nikki, Brianna is "bratty and always gets her way". Nikki also says that Brianna has an angelic face but is really a category 5 hurricane in pigtails.
Jessica Hunter is MacKenzie's best friend. She also despises Nikki because of the time Nikki opened a invitation that was for her. Jessica has blonde hair and loves the color pink.
Violet Baker is the "most popular girl" out of the most unpopular people. When she signs up to run for chairperson of WCD's halloween dance, she loses to MacKenzie Hollister and signs up for clean-up committee instead. When MacKenzie quit, Violet became head of the entertainment committee. She is said to have a large iTunes collection and is paraplegic. She first appears in the second book.
Theodore L. Swagmire III is one of the "unpopular boys" at WCD. In the second book, it was said that he had a huge crush on MacKenzie despite the fact that MacKenzie said her date to the Halloween dance was the "lead singer of the band," (who happened to be him).