An amusing secret tidbits or a hidden element written into a program or placed on a website is called Easter egg. Basically,
it is a special feature that is not otherwise made obvious, but when “clicked on”, it offers something entertaining or amusing. This may be in the form of a hidden message, an extra game level, a secret area, any funny animation, a joke, the hidden names of programmers or a surprise image of some kind. Programmers often add Easter eggs in their programs purely at their own will to add a certain extra depth to the program and to challenge their users to find it.
Any Easter egg placed in software has to fulfill following criteria;
It should be undocumented, hidden or un-obvious.
It should be re-producible i.e. every user with the same product or combination of products must be able to produce the same result given the instructions.
Programmer should have placed it only due to his/her personal reasons.
It must not be malicious in any form otherwise it will be categorized as a virus.
It should provide only entertainment to users.
Google has also placed an Easter egg to its
website and to view this Easter applet you must have Java enabled. Use your mouse to help the bunny to catch the eggs in order to spell "Google". Type following URL into your browser to enjoy this Easter egg
http://www.google.com/Easter/feature_easter.html
Easter eggs in different software or websites are not commonly known to people. These are accidentally explored or come to know from insiders. We don’t know whether such Easter eggs are placed in software with the consent of respective software companies or are placed at the sole discretion of developers but in any case Easter eggs must comply with the above mentioned criteria otherwise software company may face sever consequences if any of Easter egg proves to be malicious for any network or individual.