Control Water  Press and hold UpC or DownC at the main menu and press the analog stick. (Thank to LWargalla@t-online.de)

Different Pieces  Complete all the practice rounds, then get an OK rating in all modes, then play on any mode besides practice and collect the blue character that turns into a duck when you click on him. (Thanks to LWargalla@t-online.de)

New Grounds  Complete all the tutorials in order. Then, go to the options screen. (Thanks to Hiddenp@hotmail.com)

Smaller Pieces  Beat all modes with an expert rating. Then, start a new game and click on wetboy twice. (Thanks to Hiddenp@hotmail.com)