Speaking of famous people who are disappointing in real life, two I can think of are Roger Miller and Goldie Hawn. When I met her in the 1960's, she seemed pretty much the happy go lucky, funny lady we usually see in the movies. But later, reports from merchants on Canyon Road in Santa Fe described her as angry, arrogant, and unpleasant. They hated to see her coming. Apparently she was type casted in her role as Joanna Stayton in "Overboard".
I never met him but when I participated in "Hands across America"--I think 1986?--all resident famous personalities were invited to participate and almost all did. By putting them in the more isolated areas along I-40, it encouraged foks to drive out there to be with them. Roger Miller, however, refused to participate unless he was paid $20,000. The New Mexico organizers politely declined as the purpose of the event was to raise money to help the hungry and homeless all over the world. That struck a lot of us as major unclassy.