easter egg

A hidden element written into a program or placed on a Web site, article or television show. Basically, it is a special feature that is not otherwise made obvious, but when "clicked on" or viewed, it offers something special. It could be in the form of an extra game level or a secret area, or an animation or surprise image of some kind. Programmers often "bury" easter eggs in their programs to add a certain extra depth to the program and to challenge their users to find it.