I remember reading on one of the big tech websites (forgot which), that Flappy Bird has been around since early last year but only gained popularity just last want.  Clumsy bird appears to have hit the Play Store a day or 2 before Flappy Bird but it may be that Flappy Bird was on other App Stores like the Apple App store long before Clumsy Bird did.  Clumsy Bird game is way better than Flappy anyways so I don’t think it matters which came out first.  The author of Clumsy Bird has took down the game and I bet you he was paid very well from someone to do it so that other Clones like it can make money.