I remember walking past Brent Spiner in a hallway one year. He nodded at me, said hi and I said "Bob Wheeler, you crazy Yugoslavian knucklehead!". I'm so proud that I made him crack up.
A few years ago Jonathan Frakes sauntered past me in the vendor room as I was standing near all the double-doors leading in and out. He got to the doors and pushed once, but they didn't budge. Pushed a second time, still the doors wouldn't open. A third time... nada again. He looked up, read 'NO EXIT,' and moved a few feet over to the next bank of doors which then opened for him with ease.