There's easter eggs for the majority, however I've only been able to try KitKat, Lollipop, and Marshmallow. If using KitKat, you get a little puzzle game? I didn't like it. But if you're cool and have Andriod version 5+, aka Lollipop or Marshmallow (6), you get something cooler. Spoiler First, head to settings. You can achieve this by swiping down from the top and pressing the cog top right, or going into settings from app menu. Scroll down until you see "About Device". Click on that. Then, you click on "Software info". Here, you can see "Android version" and "5.1.1" Click on that 7 times For users on Lollipop, this is what you'll see. Marshmallow users will see similar. Click on the dot. It'll turn into a Lollipop. I've found doing a circle (anticlockwise) works to get into the game, so try that. I believe you just tap some times to get into Marshmallow's game. And here you go, you get to play Flappy Andriod. Just press the home button if you want to exit. Have fun!
Android 7.0 (Nougat) has a new Easter Egg: once you preform the regular steps you described to find an Android Easter Egg, you will find an "N". Long click it until a little cat appears, and then quickly scroll down and use the quick menu. Scroll down and click the Android Easter Egg button and drag it up. It will appear as an "Empty plate", which you can put treats to attract cats to you. The purpose of the game is to collect cats.