Don't have a whole lot of experience with celebrities, but most have been positive.
Back in my Beech 1900 days I flew Rev. Jesse Jackson and a few of his staff. Surprisingly he was quite down to earth and friendly. He was happy to chat with a couple of 20 something year old white boys for a few minutes. Not at all what I expected from him.
Flew the Smothers Brothers too (quite famous in the 60s and 70s for you younger folk), and they were quite nice.
Back in the 90s when I was working line service, a Raytheon Travelair King Air 200 came into the airport and needed cleaning. I got assigned the task. The cabin was destroyed, newspapers and garbage everywhere, food ground into the carpet, pet hair everywhere. Took a few hours to get the cabin looking good. Afterwards the pilots told me that it was Martha Stewart who made the mess. They had just dropped her off at her place in Maine. They said she was the biggest B they ever had to deal with. The reputation began long before her prison time.
A good friend flew for NetJets and he flew Jerry Seinfeld many times. He said he was okay, kind of the middle of the road as celebrities go. But he said Jerry definitely was not acting on his show, he really was exactly like his character.
Another story from my line service days. Not a famous person, that I know of, but a very wealthy person. So one day a GIV comes in and the flight attendant gets off and asks if one of us can drive her around to the airline terminal because she had to pick a kid up who was finishing his summer camp. That was the camp drop off point as most kids were airlining it home. So I drove her over to the other side. This 12 or 13 year old kid gets in with all of his stuff and the first question he asked was if his dad sent the GIV or the GV. When she replied the GIV, the kid threw a fit and complained that his dad was always trying to screw him because he never got to ride in the GV unless his dad was with him. The drive over to the other side of the airport was this kid whining about how the 40 minute flight home (we were in New Hampshire and he was flying to HPN) was going to be awful because he was stuck with the "****ty" GIV. Spoiled brat, I wanted to knock him into the next week.