Although this has probably been posted elsewhere, it was interesting to find this story on Yahoo! News of all places. Apparently, the craft developers at Google have hidden these three (although probably more) Easter Eggs in their last three Android operating systems. Here are the three in the order that these versions of Android were released:
Honeycomb Easter Egg -
The first thing to note about this particular Easter Egg is that it is Tron themed, since the movie "Tron Legacy" was out around the time the developers were making Honeycomb. Most people noticed that much of Honeycomb bore a resemblance to Tron visuals, and this hidden trick included an animation of what a Tron-ified bee would sound like. Here's a quote from the Yahoo! article with a description of how to find the Easter Egg,Gingerbread Easter Egg -Repeatedly tap on the version number in Settings -> About, and the Android mascot will take over your screen in the form of an electric blue honeybee, and make that noise in a word bubble.
In this Easter Egg, you get to see a painting of the Android mascot and a swarm of zombies. (No idea what inspired this Easter Egg) Here's how it works: Go to Settings -> About, then tap many times on the version item. Eventually the pic will pop up.
Ice Cream Sandwich Easter Egg -
Here's the final one, and unfortunately most of us will have to wait to see this Easter Egg since it comes on the soon-to-be-released Android 4.0/ICS. If you have seen the famous Nyan Cat ("Pop Tart Cat") flash animations across the web, then you will recognize this one. Once you have found this Easter Egg you get to see an animated Nyan-Droid flying across your ICS screen. Here's a quote from the Yahoo! article with details,It's really cool to see developer's having so much fun with their software. You gotta appreciate the creative flourish that amounts to a digital signature that these guys come up with. Thanks to Shadez for this tip!Repeatedly tapping on the Android version number in Settings -> About reveals the Nyandroid, as seen in this video, and long-pressing on the Nyandroid turns it into a swarm of Nyandroids that fly across your Galaxy Nexus' screen. (Right now the Galaxy Nexus is the only Android device that runs Ice Cream Sandwich.) Fan-made Nyandroid appearances include a boot animation, and a live wallpaper.
Source: Yahoo! News