Cash Cow Franchise: At least until the bottom fell out of the adventure game market in the mid-late '90s, taking Sierra with it. It typically got first dibs on any new technology as a result, which could be either a blessing or a curse depending on the game.
Fan Nickname: Among fans, the games are almost exclusively referred to as "KQ [roman numeral/#]"— with the exception of "Mask of Eternity." Fans generally call it "MoE", both because it's not officially numbered (see Numbered Sequel in the Main tab) and because it's the series' Scrappy.
The Other Darrin: Out of all four members in Graham's family, only Graham himself has not changed voice actors; the other three members are voiced by different numbers of actors: Alexander (Barry T. Smith in KQV, Robby Benson in KQVI), Valanice (Sheryl Bernstein in KQVI, Carol Bach y Rita in KQVII), and Rosella (Diana Wilson in KQV, Bernstein in KQVI, Maureen McVerry in KQVII). Cassima can also count as a new member of Graham's family, since she is voiced by Dianah Pressley in KQV, and Louise "Stevie" Vallance in KQVI.
Approval of God: At times the official canon makes references to material from the books, in manuals and hintbooks, some of the King's Quest Collections, the King's Quest trivia game "King's Questions", and Sierra's Interaction Magazine. The manual for KQ6 even utilizes Derek Karlavaegen as the author of that manual.