Easter egg...oh that's cool!

Often a developer to mark his works and make them more original and funny uses the "Easter egg", an hidden and innocuos content (completely dinstinguished from the usual functioning of the product) that can be displayed using particular commands or through a key trick or...wathever. Videogames, web applications and softwares are full of this stuff. 

To have got it across, here it it just a few examples of "Easter egg": 

Matlab - why function: 

If you tipe why in the Matlab command line, the software generates a series of random answers like these: 

>>why 

The computer did it. 

>>why 

A young kid told me to. 

Gnu/Linux enviornments - fortune command 

Open a Linux shell and write fortune in it. Proverbs, famous quote and phrases in a "fortune cookie" style will appear in the window. Some examples: 

>>fortune 

You will soon meet a person who will play an important role in your life. 

>>fortune 

Nothing so needs reforming like ad other's people habits. 

- - Mark Twain 

Mozilla - about:mozilla 

Open Mozilla, write in the address bar about:mozilla and a verse from "The Book of Mozilla" depending on the browser version will display. 

Mozilla - about:robots 

In the Firefox 3 version typing about:robots in the address bar a greeting from the robots will show up :"Gort! Klaatu barada nikto!" 

To know something more about, nothing is better than wikipedia.