Taken from Upcoming Pixar: “The concept: On opening weekend you go to see Disney’s latest movie in theatres and you could be in for a celebrity appearance.” link
Not exactly sure what this will turn out to be, so let us know here, k? However, there is a hot tip that the celebrity appearance is going to be… [spoil]Jeffrey Katzenberg.[/spoil] 
I can’t wait to fnd out what it is either.
Examples: For “Race to Witch Mountain”, Dwayne “The Rock” Johnson and the director showed up to screaming fans and for “Hannah Montana: The Movie” Miley showed up, same thing happened.
Just making a note here. In my post I pointed out that it seems like Jonas Rivera didn’t hint at any surprise appearances, instead some sort of a contest involving in-jokes…
But we’ll see.
I really hope I’m in that lucky theater…
I also heard about this via Upcoming Pixar. Like martini said, I think it involves something more than just a celebrity appearance, but a contest as well, and if the prize is what I think it is, then, I’m sorry, but it’s every man for himself…
Rachel - He’s the rumored celebrity? Ha! Why not a Pixarian? I almost don’t want to go on opening weekend now. 
– Mitch