Sorry if this has been asked, but how was it possible for all the doctors to come shift Gallifrey?
Assume in the gap between them formulating the plan and arriving at Gallifrey they set off a chain of searching for past incarnations to help them out. Because of the paradox they, too, would forget when it was over.
It was an alright episode, but there were a couple things I didn't particularly like:
Rose as the Moment's interface. I get it, she's still a big fan favorite (I dislike). Would have been better off copying ALL the NuWho companions (except Martha).
Zygons just felt like filler material. This episode should have just focused on the fall of Gallifrey instead. Instead of Zygons you could easily have had Daleks being tricky with human replicas.
The ending. It was a nice touch, but I think they should have ended this special with the death of the doctor instead. Just throw in a twist about the doctor dying at the hands of Trenzalore - an agent of Omega, who survived the time war as a result of the events of this episode. Then next season could have had 13th find his killer in addition to finding Gallifrey.
I agree about the Zygons, and it's a shame - though at least they've built some now. I look forward to their inevitable return in an episode of their own.
Regarding Rose, I get that some people don't like her, but she is the iconic one, really. Liz isn't with us any more, sadly. That torch has passed to Rose, I think. She is the iconic one. So I see why they did it, and Billie looked radiant in it (what a smile!) and put in an absolutely magnificent performance.
The British press are already complaining in reviews that the Rose character was too complicated in this episode - as in what she is. Can you imagine how those casuals would struggle if it was flickering between Rose, and Donna, and Amy? And it's sort of like the end of The End of Time, then - they always said that if one person had said no - if, say, Noel (Mickey) had been unable to do it, they'd have shelved that entire companion revisit thing. They'd have to include Martha as well, in a sense.
Regarding the last bit, eh... I'm not sure a left-field twist out of nowhere with a death or whatever would be right. I'm incredibly happy that this 50th anniversary episode stands alone and on its own as a single piece of work, as that's something Moffat's Who has strayed from a bit with pregnancies and missing babies and impossible girls and such. In this instance, it was better it was contained. We go into Christmas fresh, and I'm sure we'll get that darkness.. but ending this, a celebration, with a death or an attempt on his life would be a right bummer. It really needed to end as it did, with a sense of triumph.