This info is old, and might be outdated.
When we ate there in Dec of '07, we had a PS for the last seating (10:30? not sure). When we arrived, they let us know that we would only have the buffet, as menu ordering ended right at that time. So that's not character related, but for someone who had been drooling over the idea of one of the menu items for a month, it was rotten. (and she did NOT tell me that the chefs behind the buffet could have made it for me)
She also let us know that Chip and Dale, the hosts of the breakfast, leave by 10am, because they have "other obligations". So really we would have needed to be seated by 9:30 or 9:45 to have a chance to see them.
We did see Terk, Kenai and Koda, and Meeko.