Hmmm, my sister and I were just discussing this the other day: I don't understand how the 10K can be sold out, yet there was still availability for the Dopey. The Dopey includes the 10K, therefore there should still be room, right? ( I clearly know that there IS Not availability for the 10K, I'm not arguing that fact, I just don't understand the method that is being used)
Also, 2013 was the first year that Disney started to corral runners for the 5K races. We did it with my family this year and my sister and I were in corral A and my parents in corral B. Not sure how that was determined, but you did have to show your bib to enter the corral. I think its more for crowd control than anything else. We asked to run in B so we could be with our parents. As in any race, you can always move back a corral, but not up.