The first video game Easter Egg is commonly understood to be the inclusion of Warren Robinett's name within the Atari 2600 1979 classic Adventure. However, former Microsoft Vice President and arcade gaming enthusiast Ed Fries discovered that the 1977 sci-fi space simulator, Starship 1, had its own juicy secret just waiting to be discovered.
While interviewing developer Ron Milner for a separate project, Ron disclosed that he had hidden a message inside Starship 1, and the hunt was on. What followed was a rousing adventure, involving a rummage through the source code of the game (since Milner had forgotten how to actually trigger the secret), spending too much money for an authentic Starship 1 machine, and testing to see if the egg could indeed be accessed through legitimate means.
It's an engrossing tale, and an obvious labor of love for Fries. The full story is an adventure in its own right, and well worth a read.
[Source: Ed Fries]