Being Gus Gus would be cute. Or how about one of the fairies from Sleeping Beauty? It would be cuter if you had 2 other ppl w/ you, but it is disney related, easy to recognize, and not that many ppl go as one of the fairies. Winnie the Pooh is easy to put together or what about Edna Mode from the Incredibles?
For the past 3 Mickey's Halloween Treat, I've gone as Steamboat Willie, a 50th anniversary Disneyland custodial person, and a Dapper Dan. The Dapper Dan costume got me kicked out of Disneyland bc I "apparently" looked too much like them even though I'm a girl, my hat was made out of styrofoam, and they were wearing a different color than I was for Halloween. At least I still got to go to Mickey's Halloween Treat, but it just goes to show you how crazy strict some security ppl can be. Some didn't even care. lol.
I try to make my costumes out of regular clothes so I can go to DLR as well as DCA for the party, and so it's not a "costume" but it kinda is bc I'm portraying something else.
Hope I helped some!