“Hex confirms that, er, that our recent activities have left camiloops between our world and Roundworld, sir. That is to say, residual connections that may be used deliberately or inadvertently from either side. Magic doors, in fact, drifting without anchor. These will evaporate within a matter of days. Um…”
“I don’t want to hear ‘um,’ Mr. Stibbons. ‘Um’ is not a word we entertain here.”
“Well, the fact is that since the camiloops are spread over centuries, the Auditors may very well have been in Roundworld for some time. We have no way of knowing for how long. Hex, um, sorry, does report some circumstantial evidence that humans are dimly aware of their malign meddling, albeit at a very mundane level as evidenced by the findings of a researcher called Murphy.“

– on Murphy’s Law |
Terry Pratchett, Ian Stewart, and Jack Cohen, The Science of Discworld III: Darwin’s Watch