How to Mock a Static Singleton?

I have number of classes I've been asked to add some unit tests to with Rhino Mocks and having some issues.

First off, I know RhinoMocks doesn't allow for the mocking of Static members. I'm looking for what options I have (besides using TypeMock).

An example of the class I have is similar to the below:

class Example1 : ISomeInterface
{
    private static ISomeInterface _instance;

    private Example1()
    {
        // set properties via private static methods
    }

    static Example1()
    {
        _instance = new Example1();
    }

    public static ISomeInterface Instance() 
    {
        get { return _instance; }
    }

    // Instance properties 

    // Other Instance Properties that represent objects that follow a similar pattern.
}

So when I call the above class, it looks something like this...

Example1.Instance.SomeObject.GoDownARabbitHole();

Is there a way for me to mock out the SomeObject.GoDownARabbitHole() in this situation or mock out the Instance?