I agree with you!
Mine's 6, and has told me she wants to be Patch from 101 dalmations. Simple: white bodysuit, white tights with black fabric paint for spots!!!!
My boys usually dress in complementary costumes. For instance, Bob was a cowboy and Joey was a cow when they were 8 and 2. The next year Bob was a prisoner and Joey was a Cop. Then Bob was a doctor and Joey was the patient--complete with fake blood ALL over him.
Since we moved to Oklahoma and there is no one on our road who participates in Trick or Treat (they are the only children on the road) and they go to different schools, Joey dresses in costume for the Halloween party at school. They take candy and go from class to class for treats. I sent gingerbread last year and apple cider.
Bob usually goes over to a friends house in a more kid-friendly neighborhood and they go door to door until all the porch lights get turned off. That pale shade of green they have the next day from all that candy is priceless.