Behind the scenesEdit
The royal physicians are mentioned in KQ5 manuals (computer & NES versions), and are mentioned in-game in King's Quest VI inside the About King's Quest I-V. They are also mentioned in the King's Quest Companion.
In fact, the royal physicians were originally mentioned in the King's Quest Companion, 1st Edition. The references within KQ5 Manual and KQ6 are actually direct references to the Companion.