Seems it takes just a 3 days to and no marketing to create a smash hit like Flappy Bird which generates 50,000$ per day from ad revenue. The game elements are simply taken from Super Mario Bros. series games. The bird is very similar to flying fish in a first Super Mario Bros. game on NES. Look at the video bellow.
And all those green pipes clearly shows from where the developer got the inspiration.
Game is now removed from Android and iOS app stores due the attention this annoying and freaking hard game got. Still there is even funnier parodies of this game and much more improvement versions. If you looking at Flappy Bird alternatives you should really try these games in the video bellow.
There is still lots of unused ideas left for making more such small competitive mini indie games. I believe somebody will steal some ideas from Mario Party series and Wario Ware Inc minigames.
I am going to make a Flappy Bird clones as still I didn't published any Android game and haven't tried AdMob ads.