In the movie, Ponytail Derek is not as included as he was in the novel. In the novel, he's more of a major character. In the movie, he disappears after a scene or two. In the novel he disappears after Candace gets pregnant, which is also left out of the movie for obvious reasons. In the movie, he slaps Candace across the face and doesn't show up anywhere else in the film. Candace tells Charlie "not to tell mom and dad" about what he just saw and that "she was okay". Ponytail Derek did give Candace the mixtape at the beginning of the movie, which she gave to Charlie.