You will not even find a specific place for this, but in the guide you see the presentation times of the princesses and the places, there you go and get your autograph and photo, in the case of Michey and mini they have their theaters.
If you look at the Disney experience app it will tell you where the various character meeting spots are and times. You can even fast pass them. I can't speak to autographs because I didn't attend any of these but I would assume so.
I hate princess's and I love super cool stuff
Yes, my niece did it last month, I just dont remember the location.
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