I don't know the exact date of when Club Penguin was invented. But a few months after the Club Penguin Team (I think it was the Club Penguin Team) thought of the idea of Club Penguin, they opened the online world on the Internet on the 24th of October 2005.
Rockhopper is staff on club penguin and arrives at club penguin every 2 months. His ship is called the Migrater. Gary is staff on club penguin and Gary goes on club penguin whenever. He is usally in the secret lab when hes online.