Jacob?

I have heard a few theories about who Jacob is being played by and it's none another than Christian Sheppard. It's a good theory and I think that Jacob took on Christians body once it fell from the plane crash.

Remember that there was no body in the casket when Jack found it.

That is why I also believe that Jacob said to Locke, "Help Me." I think it my have been both Jacob and C. Sheppard asking for his help since Locke has a special bond with the island.

What are your thoughts?