Maggie Baker (Hairspray star Nikki Blonsky) is a very overweight 17 year old girl who suffers being taunted and ridiculed at school and badgered to lose weight by her thin mother (Annie Potts) who is worried she will get diabetes like her father who passed away a year prior to the beginning of the movie. The movie starts by showing what Maggie goes through every day at school. We discover that her best friend Casey (Lily Holleman) is not as unpopular as Maggie is due to her relationship with one of the popular guys. Casey is invited to a party by the boy and accepts the invite on the premise that Maggie is allowed to come as well. The popular boys cringe but don't say anything. At the party Casey is dragged away by her sort of boyfriend, leaving Maggie alone to be laughed at by the preppy click, including Liz (Liz McGeever), a very hated but feared girl at school. Maggie gets food down the front of her shirt and retreats to the kitchen to clean it off (only after being photographed eating in an unflattering manner). From the kitchen she can see Casey and her boyfriend making out in the adjacent hallway before her friend Louis (Fabian C. Moreno) greets her. It is clear that Louis has a thing for Maggie and vice versa. Louis leaves and Casey appears at the same time as Tara (Kimberly Matula) the sweet Queen Bee at school to wipe food off her shirt as well. Tara asks if Maggie is as clutzy as she is which Maggie confirms that she is. After she leaves Casey makes a remark about how Tara is only nice so she can win Homecoming Queen to which Maggie replies that it would be nice if she herself were to win Homecoming Queen and not somebody like Tara or her friends. Liz overhears and decides to nominate Maggie as a joke. The joke is on her though as many students get excited about Maggie being the queen, including Tara, who is, of course, nominated herself. Maggie easily collects 150 signatures to put her on the ballot (twice as they are stolen the first time around) and becomes an official nominee. Maggie starts campaigning but gets upset one day when she sees Tara's posters out in the hallway and imagines her mom praising Tara's thiness and beauty. She runs home to find comfort food. Meanwhile Liz vandalizes Tara's posters so the principal will think it's Maggie and take her out of the race. The plan does not work and Tara begins to suspect that her best friend is trying to sabotage Maggie. At voting time Maggie wins Homecoming Queen! The popular click is shocked and rudely sits and glares at Maggie, except for Tara who looks geniunely happy for the plus-sized beauty queen. It is later revealed that Tara voted for Maggie and not herself. Maggie is bombarded with offers from the press who wish to discuss the expierence with her. However, the popular kids are not ready to accept Maggie's win without a fight and plan to get her to resign. Tara's boyfriend Trip (Kyle Russell Clements) and Liz plot to ruin Maggie's homecoming float. When Maggie sits on it the float breaks, making it look like Maggie's massive weight broke it. Tara is outraged and breaks up with Trip. She also discovers that Liz only hangs out with her because she's popular and ends their friendship. The other popular girls stop speaking to Liz as well. Maggie goes on television to discuss her win but comes off sounding rude and ungrateful towards her friends and supporters. She has also been ignoring Casey who has been trying to ask Maggie for advice on whether or not she should consummate her relationship with her now boyfriend. Pissed, Casey spews out some harsh insults and Maggie shoves her into a row of bikes, getting herself suspended. Maggie has alienated herself from her friends and no longer wishes to be Homecoming Queen although the school tells her she can. Maggie realizes that she plays the victim and that her harshest critic is herself. She decides to go through being Homecoming Queen even though the reception will most likely be bad and asks Louis to be her King. She reconciles with both her mom and Casey who eagerly cheer her on at the game. Although many people boo her a lot of people cheer for her too. Maggie realizes that she not only won Homecoming Queen but she changed herself as well.