First videogame "easter egg" appearance awarded as a prize

In 1990, Nintendo Power magazine ran a contest in which the winner would feature in a future NES game that turned out to be The Legend of Zelda: A Link to the Past (Nintendo EAD, 1991). Hidden in the game is a room containing 45 blue rupees and a plaque that reads “My name is Chris Houlihan. This is my top secret room. Keep it between us, OK?”. It proved so elusive that its existence was largely unknown until years after the game’s initial release.