I think, it is a max from 6-8 people. You enter a small room, with Mickeys props from his cartoons. Magic books, a crystal orb and so on and a gigant trunk with stickers from the other Disney Parks and the DCL.
There is only a small gap between the trunk and the wall, were a castmember is waiting. This CM tells you when to go on. The you pass the gigant trunk an meet Mickey. All alone, execpt for the fotographer and a second CM. The other people have to wait behind the trunk til your finished. You can only have a sneek peek at Mickey while waiting absolutely next in line. All other people in the room can't see anything, only hear. But it is very quiet.
It possible, have a look at my facebook fotos, you can see the room and the props. Even with a Hidden Mickey.
http://www.facebook.com/#!/media/set/?s ... 143&type=3