Plot hole: Some episodes act as though Drake and Josh was real and some act as if it is a T.V. show. In the episode with the new principal, Helen from Drake and Josh is the same character as she was in Drake and Josh and becomes Hollywood Arts' new principal. But, in the episode when Trina's play-scene was sabotaged, Cat and Tori refer to Drake and Josh as a television show.
Continuity mistake: Every episode, the people who aren't the main characters in Tori's acting class change. Including the people in the school.
Answer: The Director hated working with Melinda, but knew that her superstar popularity and status would get his movie a big buzz and higher ratings. And the movie was discontinued for a re-audition to fill-in Melinda's leading/major role.