Nothing is immovable, therefore the immovable object must exist in a dimension outside of those pertaining to space, while the unstoppable object must exist as THE true frame of reference, so if it is moved, it isn't actually moved, the rest of the universe is moved instead. So neither object can affect the other.
Alternatively you can go with the 'unstoppable object is stationary' theory, I like both.
Alternatively you can go with the 'unstoppable object is stationary' theory, I like both.