King's Quest 0 is an fan title sometimes used to designate the very first game to take place in the King's Quest universe which went by the titles Wizard and the Princess or Adventure in Serenia depending on what computer it was developed for.
For the most part this term is avoided in any topics, and instead prefer to use a combination of "Wizard and the Princess/Adventure in Serenia", or the abbreviations of both titles. There is no plan to move the categories to Category:KQ0 or similar subcategories as of yet.
For one thing, it is somewhat misleading from the fact that it was developed before King's Quest existed, and secondly its not necessarily a prequel to King's Quest 1, and may actually chronologically take place closer to KQ3 (or a few years before KQ3). According to the King's Quest Companion, 2nd Edition its suggested that the events took place 'several years' before King's Quest V (which indicates it probably wasn't many years before KQ5, and probably certainly less than the 20 or 25 years between KQ1 and KQ5). But considering the geography of the world at the time of KQ3/4 and in the Companion for that same period, it would actually explain the shape of the continent in KQ3 (the companion, and artwork in The Official Book of King's Quest VI), as Serenia is divided into two continents as described in the prologue for Wizard and the Princess (see The North).
However, Sierra did at times describe the Wizard and the Princess as a prequel to the King's Quest games (however one wants to interpret that).
King's Quest 0 could effectively refer to the main story in King's Quest: Episode I the first episode of King's Quest: Adventures of Graham which takes place about 5 years before King's Quest 1, see KQGS timeline. However, this episode is also known as the First Quest.
Behind the scenesEdit
A number of fan developers wanted to make a remake of the game which would have given it the title King's Quest 0,and made the original title/s 'subtitles', see Intermezzo Software. Some ideas included making the wanderer a young King Edward, and Priscilla the queen who died later from the plague.