Our fair city (ok town) does a wonderful event for Halloween. On the Saturday before Halloween, the businesses in downtown throw open their doors and offer treats to the city's costumed children.
This served as a wonderful trial run for us to see if Indiana would wear his costume. He enjoyed it! When he was done (he decided that an hour of walking the pavements of old town was enough) he plopped onto a bench and started removing his costume.
We took Indy through a local haunted house, where he tried to get the monsters to pick him up. He smiled at them and giggled in delight, not the least bit frightened.
The kid is a natural at Halloween!