I met Will Ferrell, well, when I say met I got sent to a press interview to hype 'Stranger Than Fiction' thing when a friend of mine who works for Vogue couldn't go. 5 journos & Will in a room at the Dorchester (ultra swish traditional London hotel) for 1/2 an hour.
He was very funny, (funnier than the film) and not a wanky celeb at all.
Met Emma Thompson on that one also, she was nice also, and is actually alot fitter in real life than on screen...
I didn't know what the cowbell ting was about either, til I followed the link and explored.