I found the Secret

In the first level of the Black Puffle game you follow the squid and make sure your catching each bubble as you go. and when you keep going you may get to here :

Then you follow the road and you will get to an entrance once you get into the entrance you get into a special room with nothing special in it just a black key (pin) and you cant use it for anything else. But it is a pretty cool room to play hide n' seek with your friends.