Doug, Terry Pratchett was also known as "Pterry" so when he became Sir Terry Pratchett he obviously would then also be known as "Sir Pterry".

There would not be one *single* reference to monarchy. There would be references scattered throughout many of his books to monarchy or aristocracy, people in power etc.

It's kind of an in-joke to reference Pratchett in relation to any farcical, nonsensical situations relating to life generally or people in power doing doing eye-wateringly bewildering things which throw the lives of rest of the people into chaos. Hence the connection in the minds of Pratchett's fans to the Trump situation as it unfolds.