Mickey's Not So Scary Halloween party kicks off on September 10 at the Magic Kingdom. It's a hard ticketed event that runs on select nights after the park closes. Yes, you do get to ride the major rides, but the party's appeal lies in all the special treats, both literal and figurative.
You can see some of the Halloween decorations during the day (get a sampling in this article), but the park is transformed at night with costumed characters, special entertainment, and lots of candy. If you'd like to see some scenes from the party, check out the list accompanying this article.
The party is also the one time of year when everyone, of any age, can wear a costume to the park. Normally that's restricted to young kids, but teens and even adults can deck themselves out as their favorite characters or whatever else they wish. It's as much fun seeing what your fellow guests are wearing as it is seeing the official characters.
Check out the list accompanying this article for a brief taste of the fun.