Typemock & JustMock are 2 commercially available mocking tools that let you achieve something that should be impossible. Unlike all other mocking frameworks, they let you mock sealed classes, static and non-virtual methods, but how do they do this?
There is an update to this post, based on feedback I received.
At Build 2014 Microsoft open source their next-generation C#/VB.NET compiler, called Roslyn. The project is hosted on codeplex and you can even browse the source, using the new Reference Source browser, which is itself powered by Roslyn (that’s some crazy, meta-recursion going on there!).