...there was a theory that circulated a couple of months ago that the whole Titanic thing is in the Doctor's head and has been created as a result of the TARDIS going loopy after the Master's fiddling with it, and Astrid is actually the Tardis guiding the Doctor out of the 'false reality', and the Porg (or whatever the villain is) is the 'fault'
Its quite a good theory, and I wouldn't mind at all if that were the case.
