It's bascially a family-oriented Halloween event. There are special Halloween versions of Clyde and Seamore, Pets Ahoy, and Shamu Rocks America. There's also about 20-30 candy stops where kids can pick up sweets. There's also a small costume show. Kids can come to the park dressed up. I'm not sure about adults. Otherwise, I'll be wearing a Microsoft Borg outfit.
I went on Saturday and it was fairly crowded, but not too bad. The event runs on a Friday, Saturday, and Sunday, so go on a Friday or Sunday to beat the crowds.