I've noticed that when you try to add an anime to your watchlist that is already on your watchlist, you get the
following Database Error:
Quote: There was an error with the database. If this problem persists for more than 10 minutes, please make a bug report.
If you think an error has occured, please make a bug report in the forum.
Return to the Minitokyo homepage.
Looks to me as if Sheqel forgot to make a function that checks if a show is already in your watchlist or not XD
