PatH - my favourite is definitely "Witches Abroad."
"Magrat has adopted trousers as practical wear for travelling by broomstick.
'I don't 'old with it,' said Granny Weatherwax, 'everybody can see her legs.'
'No they can't,' said Nanny, 'the reason being, the material is in the way.'
'Yes, but they can see where her legs are.' said Granny Weatherwax.
'That's silly. That's like saying everyone is naked under their clothes.' said Magrat.
'Magrat Garlick, may you be forgiven,' said Granny Weatherwax.
'Well it's true!'
'I'm not,' said Granny flatly, 'I've got three vests on.' "
P.S. - Do I get commission??