"According to Wikipedia, the name Easter egg comes from Dan O'Bannon's horror spoof, Return of the Living Dead. In the film, a container of zombies goes missing and is referred to--in code--as an "Easter egg." Of course, the name is more obviously derived from "Easter egg hunt" fame, where Easter-celebrating-children are made to search through an established area (usually the yard) for dyed hard-boiled eggs or plastic eggs filled with candy. Generally (in video games at least) Easter eggs are a reward, not a punishment, although they range from hidden files to secret rooms and often break character from the game, making reference to the developer or to the notion of the Easter egg itself. It's important to distinguish Easter eggs from cheats, since the former represent additional content. However, they're usually superfluous to gameplay. Cheats like the famous "Justin Bailey" code from Metroid may be as notorious as some of the more notable Easter eggs, but they serve a specific function, such as skipping gameplay levels or invoking invincibility. We define Easter eggs as hidden properties of games that can be revealed by button combinations or by accessing remote areas in the game or on the disc itself." [more]