I have my own Jack Nicholson story. He was filming a movie that took place in my hometown, I think it was Something's Gotta Give.
Anyway, they were shooting in the store that I worked at and I'm there just to keep an eye on things. Jack Nicholson lights up a cigarette in a fucking TOY STORE. I say "I'm sorry, but you can't smoke that in here.".
At first I figured he just wanted to do it where nobody would bother him so I followed up with "if you want, you can go out back. There's no public access there."
He said "Don't you know who the fuck I am?" and put his cigarette out on the floor.
Golfing at a celeb/police fundraiser event, met many celebs that day, but what stood out was Jack Nicholson. I tried to approach him (I was a kid at that point) and he raised his club as if threatening to strike me with it. I think every camera on the golf course raised at that moment, so he just made another gesture and a sneer at me and got in his cart.
Sometime later, my dad was selected as part of the backstage security provided by the LAPD for the Academy Awards. He spent most of this talking to random celebs as they wandered in and out of the area. I warned him about Nicholson; so when he got home we eagerly awaited his summary.
"Celine Dion wouldn't look up, she followed her bodyguard's feet and ignored everyone. Robin Williams talked to me for half an hour, he was really cool. Jack Nicholson was a jerk, like you said, and Helen Hunt was a complete bitch to everyone."
I had a dog (Walter) who hated Jack Nicholson. I found this out when I showed the movie The Shining to my then girlfriend. The whole move Walter growled until that scene where Jack comes busting through the door. My dog lost his composure, flipped off the couch and hid under the bed growling for the remainder of the movie.
Months and many more Jack Nicholson movies later I am walking Walter down the sidewalk when he starts twitch and growl. He is well trained and never does this in public. I scan around to see what he is freaking out about and coming at us is Jack. I can't think of anything else to say so I blurt out "I am sorry Jack. My dog just hates you." He smiles at me then delivers the best creepy face he can on short notice to my dog which sends Walter in to a full blown rage. Off goes Jack down the road.