Whilst I haven't had any notable brushes with Classical musicians of renown, my mother told me a story about a friend of hers.
One weekend, world famous oboeist Leon Goosens came to stay with my mother's friend. Her six year old son came into the room with a toy penny whistle and said to Goosens, "Bet you can't get a tune out of this!" He took the penny whistle and proceeded to play a lovely little tune. At the end, the little boy said "Oh, I'm glad it still works - it's been down the toilet all day!!" PaulC