We went to Mickey's Halloween Treat at Disney's California Adventure two years ago. It was our first trip ever to DLR, and since my DDs birthday is on Halloween, we felt it was a great time to go. We went to the party on Halloween. There are a lot of Trick-or-Treating stops. There are a lot of villains out and about, and you can catch your favorite Disney characters dressed up for Halloween. It was fun. The candy was pretty good. Some good chocolate candy and then some of the cheap stuff, too. Would we do it again? Yes! In a heartbeat.
My TR details the day. If you start on page 10, you will see the Halloween decorations at both parks. Page 12 starts talking about Mickey's Halloween Treat.
Sing with me...California Here We Come! Days 7 & 8, updated 12/20
Have fun!