Go into settings, then scroll down and select "About phone" (or "About tablet" is appropriate). Repeatedly tap on "android version" and a lollipop will, er, pop up. Next, tap and hold the lollipop a few times. You will see an animation each time - when you do, tap and hold again. After 4-5 times, I forget the exact number, the Flappy Android game will appear. Waste time as needed.