A while ago I found I wanted NMock to allow me to specify what a mock object should return without setting up an expectation.
SetResult lets you do this, but I wanted the return value to change depending on the parameters. So I hacked the source code a bit and came up with this.
The new syntax is
DynamicMock mock = new DynamicMock(typeof("Banana"));
mock.Return("MethodName",returnValue,param1, param2 ... );
Feel free to try it out. No warrenty is provided.