Easter Eggs in King's Quest I: Quest for the Crown (SCI)
Egg id: 417
At the gate which leads to the land in the clouds, try to "pick lock" for a reference to the "Famous Adventurer's Correspondence School", which is a reference to Quest for Glory 1 and 2.
When you're in the nest of the pterodactyl on Estros, wait a bit and at one point you'll see King Graham fly by, a reference to him taking a flight with a condor in King's Quest 1.
In the preservation lab, Vat 14 contains King Edward of King's Quest (see also the listing of the vat contents on the desk of Ernie Leech). Vat 10 contains the unicorn from King's Quest 4. Vat 9 contains lemmings.