"You don't know when you're being watched. That's one of the weird things about celebrity. It's my least favorite part of acting, celebrity"

Denzel Washington is expressing his distaste for the lack of personal privacy that includes being a star. He is saying that you never know when you are being seen, which can be a tough thing to handle. He is implying that it is a weird part of being a star, and it is something that he does not take pleasure in. He is highlighting the fact that stars are constantly under scrutiny and that it can be tough to live a normal life when you are constantly in the public eye. He is emphasizing that celeb is his least preferred part of acting, as it removes his personal privacy and makes it challenging to live a typical life.