Disneyland at Halloween
In 2006, Disney started getting gussied up for Halloween, with special fall-and Halloween-themed decorations. Pumpkin Mickeys sprout up everywhere, including a 16-foot-tall Mickey Mouse jack-o-lantern on Main Street that's a perfect backdrop for a photo. The Haunted Mansion takes on its “Nightmare Before Christmas” décor for the event, with a special holiday effect replacing the hitchhiking ghosts that normally appear near the end. The characters don their Halloween costumes, and you can buy special jack-o-lantern Mickey ears as a souvenir.
The Halloween festivities start in early October, and the park gets extraordinarily crowded on the first day the decorations are up. If you want to see it on opening weekend, go on Sunday.