When Peyton and Brooke leave the store after taking the shirts with Brooke's designs on them, an alarm goes off. The alarm only goes off if there is a sensor tag on an item, and none of the shirts the girls took had sensors on them.
In one episode, Brooke calls Peyton by her full name "Peyton Elizabeth Sawyer" (her mother even says that her middle name is Elizabeth). However, when Peyton goes to get Haley, when Haley is with Chris, Peyton tells Haley how, lately she's been angry, and Peyton says that Brooke calls her "Peyton Marie Sawyer - PMS". PMS is just a joke, it is established that Peyton's middle name is Elizabeth, after her birth Mother Ellie- Elizabeth