I think I found a glitch, but I'm not sure. When you click to buy an item and choose what duck you want it on, but click cancel, I think you lose your money anyways.
If the developer is to throw away credits to everyone, then he should give us 1 credit everytime we level up. That way, we can be lucky enough to get something that should've cost us Kreds, and the developer can still benefit something outta his game! Everybody wins. :D.