"Who is Mike French, Mummy?"
"What is Blue Friday, Mummy?"
"Can you write a note in The Hobbit for my friend?" (Yes really)
"Sorry, I would but I've never heard of you."
Arh the fame - er not quite - but still had some great conversations and did sign a load of copies in the end :-)
And here especially for you is a I've Signed at Waterstones template - just add in your own image and books - and heh presto - just post it on facebook and tell all your mates that you are famous.