Continuity mistake: When Chase comes to talk to Zoey at the end of the episode when they are getting ready to watch the show on TV. The camera is on Chase and we see someone coming down the stairs and the camera goes to Zoey then back to Chase the same person is again coming down the stairs.
Continuity mistake: In season 2 episode 5, Zoey, Chase, Dustin and Nicole are eating lunch. Trisha joins them later on, and sticks gum to Dustins' drink. The gum changes sizes and moves between shots.
Revealing mistake: Logan gets all the characters to spend spring break at his dad's house. When Zoey finds out Dustin drank all of Quinn's "fratz" she screams his name and runs to go and find him, but despite being meant to be angry you can tell she's laughing.
Answer: Dustin was only considered a main character from season 1-3, and probably just because he's Zoey's brother. Dana was only a main character for season 1 and James didn't become a main character until season 4.
Bishop73