Even in the era of social media, most celebrities tend to keep their public and private lives fairly separate. So even if we think we know famous people, we probably don't know that much about who they really are. Unless we happen to work at a restaurant or bar that they frequently patronize.
People who work in the service industry often get unique insight into the lives of the rich and famous. Especially because you can learn a lot about a person by how they treat their waitstaff.
In a popular Reddit list, someone asked: "Waiters and waitresses, have you ever served a celebrity and what was it like serving them?"
1.) From faw-q:
Will Ferrell- I was a bartender at the time, he was in town for a stand up gig with Demitri Martin, Zach Galifinakis and Nick Swardson. We shut down half the bar for them and their crew for a football watch party. I remember Nick didn't even watch the game, he played buck hunter the entire time. They all kept to themselves and were all generally quiet. Will was the only one really known at the time.