Brett is a classmate and friend of Stephanie's who plays Little League Baseball for the Cubs.
D.J. teases Stephanie about her interest in Brett, such as when Stephanie clenches her heart, and says her heartbeat feels like "Brett-Brett, Brett-Brett". In the episode "Stephanie Plays the Field", Brett asks Stephanie to go easy on him with the "Tanner Twister", a method of pitching created by Stephanie and her father. Though she struck him out later in that episode, she thinks he is mad at her. Brett said he would have done the same thing. They still remained boyfriend and girlfriend, although he is never mentioned again after that episode.