Isn't the Hallowen Party like the Christmas Party? I think it is a private ticket event. You don't need a regular park ticket unless you want to enter the park earlier in the day. The Halloween Party ticket IS your park ticket for that evening, but it won't allow you admisson until late afternoon. If you are already in the park from ealier in the day, you don;t have to leave, but will be "herded" to the tomorrowland area until the regular day guests are out of he park. But, if you do enter the park earlier in the day, you will have to get a wristband, they usually start distribution after 4pm in front of the castle.