Way back in 1990 we were in MGM and I saw a man sitting on the pavement with a little green foot under his arm. I said to my friend "wonder who that is". Around turned Jim Henson with Kermit the Frog, who he stuck in my face and said Hiiiiiiiiiiiii, in that Kermie voice. I totally freaked started screaming IT"S KERMIT!!!! I ran into the Men's Room while DH was in there and jumped on his back screaming. He carried me out and by this time they had security around poor Jim Henson.
I would probably freak again if I saw Kermit and Miss Piggy.
The other part of the story is that I just had lectured my friends to not cause a scene when they see celebs, since we had just spotted Micheal Eisner and George Lucas. It was the day that Star Tours opened.