"Multiple exclamation marks, he went on, shaking his head, are a sure sign of a diseased mind."
(Terry Pratchett in "Eric")
"Five exclamation marks, the sure sign of an insane mind."
(Terry Pratchett in "Reaper Man")
"And all those exclamation marks, you notice? Five? A sure sign of someone who wears his underpants on his head."
(Terry Pratchett in "Maskerade")