Good: Suzie Quatro. Very friendly, courteous and even entertained the first few rows with a story of a flight she had with Alice Cooper.
Odd: Joan Armatrading. She didn't make eye contact and whenever I spoke to her, she whispered the answer to her PA, who then answered me. "Me, myself, I" indeed! She means "Me, myself, I and my PA". She gave me the willies...
I usually find the celebrities themselves aren't as bad as their PA-s and minders. Case in point, President of Ireland on a visit to Australia was just gorgeous, but her PA-s and some of her entourage were among the biggest pack of idiots I've had on a flight. Not the best ambassadors for the Republic.