OK so I'm so confused! Do you need to refridgerate buttercream that has real butter in it and heavy cream? What about peanut butter filling with peanut butter, butter, sugar and heavy cream? I'm new to all this and hate refridgerating cake especially when I cover them in fondant! But I also worry about making family and friends sick with my cakes!!

There's generally enough sugar in buttercream and fillings to act as a preservative and keep bacterial growth from happening. You don't need to refrigerate you cakes just because your buttercream and peanut butter fillings have cream in them.