Get ready for some arguments, because this week's poll is a controversial one!!!
I think he was originally intended as one, and the person who suggested this poll (Scoobyfan4ever) brought up an excellent point here. Queen Morbidia is never said to be one of the 13 ghosts either, and is just a vampiress who wants the chest for herself. I think the difference as to why people think she's one of the ghosts, but not Captain Ferguson, is because we see Queen Morbidia (or her ashes, at least) put into the chest directly, whereas the captain gets caught up in the cyclone ghost's tornado along with all the other ghost passengers, so we never physically see him get put in the chest.
That's my theory, but I wanna hear all of yours!
Here's the results from last week's poll!
Who is your favorite guest star in What's New Scooby-Doo?
Simple Plan - 38
Lindsay Pagano - 10
J.C. Chasez - 6
Chris Klug - 3
Mike Piazza - 3