Android
Android 4.0 Ice Cream Sandwich
Google plays off pop-culture's favorite (and most annoying) flying kitty, Nyan Cat, with Nyandroid. To make this fun animation appear, go to Settings, About, and then keep tapping the Android version number until Nyandroid appears.
Android (4.1, 4.2, 4.3) Jelly Bean
In this Easter egg, Google gives you a mini-game that lets you endlessly flick little jelly beans off the screen. Simply go to Settings, About Phone, and keep tapping the version number until you see a smiling red bean. Tap on it, and then let the game begin.
Android (4.4) KitKat
In KitKat, Google creates a fun sliding tile game with pictures of different sweet treats. To access it, go to Settings, About Phone, and, once again, keep tapping the version number, but this time you'll see Google's signature chocolate bar. Tap on it, and the tiles will appear!