What was the first hidden video-game Easter egg, placed in Atari's 1980 game Adventure?

The first widely recognized video-game Easter egg was Warren Robinett’s hidden name in Atari’s Adventure.

Robinett secretly placed the message “Created by Warren Robinett” inside the 1980 Atari 2600 game. Players could reveal it by finding a concealed room, reached through a particular sequence involving a nearly invisible object and a specific area of the game world.

Atari did not routinely credit individual programmers on its game packaging at the time. Robinett added the signature partly because he wanted recognition for his work. The company learned about the secret after the game had shipped, but decided that removing it would cost more than leaving it in released cartridges.

The discovery gave the practice its familiar name: an Easter egg, meaning a hidden surprise intentionally placed by a creator. Later games used secret messages, rooms, characters, and developer references, making hidden content a lasting part of video-game culture.