Easter Egg

A virtual Easter egg is a 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.

Usually, such Easter eggs come in the form of a hidden character, scene or reference to something else outside the subjects area (for example a tribute to a series that is hidden in a secret area). Due to legal reasons, many companies invoked strict rules about Easter eggs, not only for copyright reasons but also due to the problems having something in the game that has not been announced openly.

The Different Kind of Easter Eggs.
Oda is renowned for featuring many different kinds of Easter eggs in One Piece. The most famous and frequently seen kind of easter eggs are the joke characters (also known as easter egg characters). The most notable joke character is Pandaman who appears throughout the series, in several different guises and incarnations. Other kinds of easter eggs are the fictional brands like Doskoi Panda and Criminal, but also the slight references to Oda himself seen for instance on spines of books.

Trivia

 * The Easter Eggs have their own ongoing story on the inside back cover of each Volume starting at Volume 25 starring Pandaman.