Theory:Doctor Who television discontinuity and plot holes/Orphan 55


 * Why didn't the TARDIS translate that Russian sign for Graham and Yaz?
 * Maybe because they were too far away from it.
 * Agreed. The TARDIS didn't go with them, possibly leading the translation circuitry to disconnect. Or maybe the transportation cube was responsible.


 * Why does Ryan address Graham by name, after having decided to call him "Granddad" by the end of Series 11?
 * It’s been established in other stories (as recently as Spyfall in fact) that Ryan uses Graham and "Granddad" interchangably on occassion.


 * 1). How can the world be uninhabitable in the lead-up to its destruction when The Sontaran Experiment showed that it was still inhabitable?


 * 2). How can the future be "only a possibility" that can be avoided when it has been shown on multiple occasions that the exact opposite is the case?
 * I agree. There are fixed points in time in the future that conflict with this episode.  Perhaps they are somehow not in their own universe any more (Tennant's Dr went to the Doomsday universe in Journey's End).  And perhaps the transport they used that took them to Orphan 55 came from a parallel universe.  Maybe Tennant brought it back from the Doomsday universe. If so, and since the Dr was surprised that Orphan 55 was earth, then she was probably shocked that this happened to Rose's new earth.  Also, that would mean that she knew it wasn't the earth from her universe and that this isn't one possible future.  Perhaps it's what she thought the companions needed to hear.  Which means she lied about "one possible future", but that would be rule #1.  The Dr lies.
 * I don't really think it's as big of a discontinuity as people make it out to be. Possible futures have been explored before (Haemovores), and the Doctor may have been lying (or telling a half-truth) at the end to comfort her companions. They also saw only some aspects of the future, so while Orphan 55's existence might be fixed, other details can still change. Perhaps Ryan or Yaz or Graham say something, based on their experiences, that encourage people to eventually form a group that prepares ways to restore the planet after its destruction, at an earlier point in time than it might have done had the Doctor not taken them here.
 * It's weird, but there are possibilities to explain what happened. In The Sunmakers the population of Earth has moved to Pluto because the resources of Earth were depleted by the Usurians. In The City of Death the Doctor shows Romana an alternate reality in which the Jagaroth have devastated Earth. But continuity is so buggered up already after 57 years so another twist isn't going to make much of a difference. Maybe BENNIIII !!!! knew the answer.