A virtual Easter egg is an intentional hidden message or feature in an object such as a movie, book, CD, DVD, computer program, or video game. The term draws a parallel with the custom of the Easter egg hunt observed in many Western nations, but actually is derived by the practice of the last Russian imperial family's tradition of giving elaborately jeweled egg-shaped creations by Fabergé which usually contained hidden gifts themselves.
This practice is similar in some respects to hidden signature motifs such as Diego Rivera including himself in his murals, Alfred Hitchcock's legendary cameo appearances, and various "Hidden Mickeys" that can be found throughout Disneyland. An early example of these kind of "Easter eggs" is Al Hirschfeld's "Nina."
Atari's Adventure, released in 1979, contained what was thought to be the first video game "Easter egg", the name of the programmer (Warren Robinett). However, evidence of earlier Easter eggs has since surfaced. Several cartridges for the Fairchild Channel F include previously unknown Easter eggs, programmed by Michael Glass and Brad Reid-Selth, that are believed to predate Robinett's work. The 1978 Atari arcade games Orbit and Skydiver also include Easter eggs, programmed by Owen Rubin, though unlike Glass and Reid-Selth's eggs, the method of triggering these has yet to be discovered. Despite this evidence of prior art, Robinett's egg was certainly the first of its kind to be discovered and, consequently, the first Easter egg to come to widespread attention.
Easter eggs found in some Unix operating systems caused them to respond to the command "make love" with "not war?" and "why" with "why not" (a reference to The Prisoner in Berkeley Unix 1977). The TOPS-10 operating system (for the DEC PDP-10 computer) had the "make love" hack before 1971; it included a short, thoughtful pause before the response. This same behavior occurred on the RSTS/E operating system where the command "make" was used to invoke the TECO editor, and TECO would also provide this response.
The largest Easter egg is purported to be in the Atari 400/800 version of Pitfall II: Lost Caverns, which contains an entire game that was more complex and challenging than the original Pitfall II. Many personal computers have much more elaborate eggs hidden in ROM, including lists of the developers' names, political exhortations, snatches of music, and (in one case) images of the entire development team. Easter eggs in the 1997 version of Microsoft Office include a hidden flight simulator in Microsoft Excel and a pinball game in Word (see Easter eggs in Microsoft products). The Palm operating system has elaborately hidden animations and other surprises. The Debian GNU/Linux package tool apt-get has an Easter egg involving an ASCII cow when variants on "apt-get moo" are typed into the shell. Many new video games contain easter eggs, like Microsoft's very popular Halo series.
An Easter Egg is found on all Microsoft Windows Operating Systems prior to XP. In the 3D Text screen saver, entering the text "volcano" will display the names of all the known volcanoes that exist in the world. Microsoft removed this Easter Egg in XP but added others. One which continues till Windows XP is to simultaneously hold the Alt, shift, and the number 2 keys in the Solitaire game to produce a forced win.
A number of early Microsoft programs had hidden animated stuffed animal characters which could be revealed by following a complicated sequence of inputs. An early version of Microsoft Excel contained a hidden Doom-like action game called "The Hall of Tortured Souls". Windows 3.1 has a hidden developer credits page, which can be accessed by following a sequence of right-clicking and entering code words which is passed around by word-of-mouth.
Perhaps the most famous example of a hardware Easter egg is in the HP ScanJet 5P, where the device will play the Ode to Joy or Für Elise by varying the stepper motor speed if users power the device up with the scan button depressed. This is achieved through software intervention. Another Easter egg is found in the Kurzweil K2x musical keyboard series (K2500, K2600 and others): if users type "Pong" while in search mode they can play the game Pong. The EEPROM of Nagra smart cards for the Dish Network satellite television system contain the phrase "NipPEr Is a buTt liCkeR". Nipper was a hacker who broke old security routines on the cards, and this text is included as a fallback to old security routines, where the phrase was hashed against an input text to verify the card. Several oscilloscopes have been known to contain Easter eggs. One example includes the HP 54622D known to have Asteroids clone (and even saves high scores in NV-RAM).
Originally, the Easter eggs served a useful purpose as well. Not unlike cartographers who may insert trap streets or nonexistent landscape features as a copyright infringement detection aid, IC designers may also build non-functional circuits on their chips to help them catch infringers. Easter eggs, however benign, if directly copied by the defendant, could be used in mask work infringement litigation. Changes to the copyright laws (in the USA, the Semiconductor Chip Protection Act of 1984, and similar laws in other countries) now grant automatic exclusive rights to mask works, and the Easter egg no longer serves any practical use.
Western Digital's MyBook Pro has several words on the metal band that wraps around 3 sides in Morse Code. The code reads:
PERSONALRELIABLEINNOVATIVESIMPLE
INNOVATIVEPERSONALDESIGNRELIABLE
INNOVATIVEDESIGNPERSONALDESIGN
SIMPLEINNOVATIVE
The Commodore Amiga models 500, 600 and 1200 each featured Easter eggs, in the form of titles of songs by The B-52's etched on the motherboards. The 500 says "Rock Lobster", the 600 says "June Bug", and the 1200 says "Channel Z". The Amiga OS software includes a variety of hidden messages as well.
Several models of S3 Trio 64v+ graphics cards have lyrics of songs by The Beatles printed faintly along the edge of the card.
The circuit board under the bottom most plate of HP LaserJet 1100 printer has the following text printed on it: "This Product is Dedicated in Memory of our Good Friend Ming-Zen Kuo".