I realize that the King's Quest series has forever secured itself in the adventure genre, but anyone who played the earlier installments (particularly King's Quest III and the spells you devised in the wizard's basement) will no doubt realize the influence that RPGs had on the titles. As such, I found Good Old Games' new "From Monochrome to Monarchy: The History of King's Quest" article to be excellent reading:
William was entranced with the sights and sounds of the caves. As he meticulously composed plotter-line-drawing maps of the sprawling caverns he and his wife had traversed, William allowed his imagination to run wild, christening each area with whimsical names such as "The Hall of the Mountain King" and "Twopit Room". The release of Dungeons & Dragons in 1974 fueled William's already active imagination. Captivated by the pen-and-paper role-playing game's limitless possibilities and fantastical adventures, William became known among his circle of gamers as "Willie the Thief".
In 1975, reality caught up with William. The Crowthers divorced, and their two daughters went to live with Patricia. William missed his daughters terribly, but rather than sink into a mire of loneliness, he set about building a project for the girls to enjoy when they came to visit. Armed with knowledge of FORTRAN, a Digital Equipment Corporation PDP-10 computer, and the stacks of documents and maps he'd composed while spelunking through Kentucky's caves, William wrote lines and lines of code that eventually comprised Adventure, the first computer adventure game.
Rather than again dip into her dark side for the next installment in On-Line's Hi-Res Adventure series, Roberta Williams chose to draw from the fairy tales she had cherished since childhood to create a world that encouraged a sense of whimsy rather than danger. Thus was the realm of Serenia born, a kingdom that would one day play host to a character that would arguably become Roberta's most beloved.
Just as Mystery House had innovated adventure games by displaying black-and-white line drawings to accompany text, Roberta Williams continued breaking ground with her new game, entitled Wizard and the Princess, by injecting the game with color. Such a move required technical finesse: because the Apple II was only capable of displaying six colors at a time, a graphic processing technique known as dithering had to be applied. Used to create an optical illusion that fools the eye into seeing more colors than those presented, dithering is accomplished by diffusing colored pixels. Picture a checkerboard pattern of red and blue squares. If the squares were to be gradually made smaller, the eye would eventually perceive the color violet due to the adjacent squares seeming to blend. The Apple II hardware was up to the task, and Serenia was portrayed in Roberta's intended vibrancy.