Which event allows guests to dress in costume at Disney parks?

The event that allows guests to dress in costume at Disney parks is Mickey's Not-So-Scary Halloween Party. During this special event, guests of all ages are encouraged to wear costumes while enjoying the Halloween-themed attractions, entertainment, and character meet-and-greets. This celebration offers a unique opportunity for attendees to express their creativity and immerse themselves in the Halloween spirit in a family-friendly environment.

Mickey's Not-So-Scary Halloween Party features special entertainment elements such as a themed parade and fireworks show, making it a beloved event for many guests who appreciate the chance to dress up and celebrate in a whimsical setting. The event does have certain guidelines for costumes to ensure safety and appropriateness, but overall it is one of the few occasions at Disney parks when dressing up is widely accepted and encouraged.

In contrast, other options like the Disney Family Celebration, Disney's Spring Fling, and Holiday on Ice do not specifically promote or allow guests to wear costumes, focusing instead on themed activities or performances. This distinction highlights why the Halloween party stands out as the primary event for costume-clad guests.