I am not sure if this is the proper name for those things, but I heard it around so. I am talking about those hidden games or tricks that you can find online on embed in the code of games and software. Google has its share of them, and the guys from MakeUseOf created a list with the best ones.
For example if you hold Click [CTRL] + [ALT] + [A] in Google Earth you will launch a flight simulator!
The other list items are pretty funny too.
The only flaw is that they missed my all time favorite. Go to Google.com, type “find chuck norris” on the search bar, and click “I am feeling lucky.” You will see the result!