(Major spoilers for episode 12 of Doctor Who Series 5.)Item 0: SQUEEEEEEEEEEEEEEEEEEEEEEEE! Ok, now that that's out of the way...
Item 1: It almost seems like Moffat is trying to beat RTD at his own game here. Not only is the penultimate episode of the series a grandiose opera that brings back everybody and everything it can, but it actually finds a way to up the stakes of The End of Time. Russell T Davies' first finale put a future Earth in jeopardy (the Daleks returned). His second did the same with present day Earth (Daleks + Cybermen). The third year, he actually did devastate the Earth, all of which had to be reset (the Master returned as did Jack). The fourth series threatened to end all realities (with the Daleks, Davros and almost every member of the supporting cast including lost Rose). The End of Time pulled the same trick, starting with humanity and then going outward, this time with the Time Lords, the Master and yet again, all the supporting players. Moffat goes the extra length and makes EVERY Doctor Who monster return and this time, the universe is actually extinguished on screen. We've had desperate, crazy cliffhangers before, of course. Only Last of the Time Lords can really be called a frustrating disappointment, but deus ex machina and/or silliness has plagued many other finales. The Pandorica Opens is probably the best penultimate episode we've had, and I hold out hope that it'll be a killer finale that ties beautifully into the rest of the Series. That's my feeling right now.
Item 2: Already, The Pandorica Opens has many call-backs to earlier in the series. Van Gogh, Churchill & Bracewell, Liz Ten and of course River, all make an appearance. This actually makes me believe the "future Doctor" theory that's been mentioned in these reviews could play itself out in the finale. They obviously filmed extra stuff with the stars of each episode.
Item 3: River Song continues to be a charm of a character, and we learn a little more about her here. This is earlier than The Time of Angels (as per River telling the Doctor they'd meet again when The Pandorica Opens), and she starts the story in prison. Her message to the Doctor this time is a pretty cool reference to Hitchhiker's Guide, but the laugh out loud moment for me was the prison guard pointing his gun at a doodle. Oh, hallucinogenic lipstick! As for her relationship to the Doctor, it is coming into focus as a truly romantic one. As she fails and the TARDIS explodes, she says "I'm sorry, my love."
Item 4: Amy's storybook life. If River is an enigma, I'm not sure what to think about Amy either. The Doctor tells her her life doesn't make sense and wonders why (huge house, no parental units, and of course, the effect of removing Rory from the timeline can't help). In this story, the Doctor's enemies have used Amy's psychic residue to create a trap. It uses her favorite time period and myth, even reproducing images from her picture books (including a picture of Rory in a Roman costume). I keep thinking back to The Eleventh Hour when the Doctor said Amelia Pond is a name from a fairy tale. Is anything about Amy real? And if not, how is that possible? Of course, the Doctor is treated as myth too. Legend says the Pandorica holds something dangerous, perhaps a trickster god. And by the end, it does. It sheds light on River's amusing "Aren't we all?" to the Doctor's "The Pandorica? That's a fairy tale" in Time of Angels, doesn't it?
Item 5: The Grand Moff is very cruel to give us back Rory and then to wrench him away again. Or has he? We've learned from this series that love can transform a machine into a man (Bracewell), and Amy attempts this here. Furthermore, the Doctor says remembering someone can make them real again. And Auton Rory (another Mickey comparison, plastic boyfriends) does seem to remember his death, which surely isn't part of any psychic residue found in Amy's house (or in the universe, since he's been erased). Is this Rory's soul that has somehow found its way to the Auton body? And does it matter, since the universe has been extinguished. If the Doctor fixes the universe and, I dunno, makes the cracks eat themselves, won't that reset Rory's erasure?
Item 6: So... Who are all those aliens? I've got a full list for you, whether name-dropped or appearing in the final scene (some only visible in the Doctor Who Confidential):
-Blowfish (from Torchwood, what they heck are they doing here?)
-Chelonians (I squeed, these military turtles were created by current series writer Gareth Roberts in the New Adventures novel The Highest Science, and have never appeared on tv - nor here, but they are mentioned)
-Cybermen (see item 7)
-Draconians (from the Pertwee era; these aren't enemies of the Doctor)
-Drahvins (from Galaxy 4, a 1st Doctor story; they are basically an Amazon race)
-Hoix (the meat eater from Love & Monsters)
-Nestenes (and their Autons)
-Silurians (or I should say the new Reptilians from The Hungry Earth; these are an odd choice)
-Slitheen (only mentioned thankfully)
-Terileptils (from the 5th Doctor story, The Visitation)
-Uvodni (from Sarah Jane Adventures' The Warriors of Kudlak)
-Weevils (from Torchwood, again, a strange choice)
-Zygons (from the 4th Doctor story, Terror of the Zygons)
Sadly, the classic series call-backs are just references and not full blown appearances. It is very much as if they grabbed every possible costume in the wardrobe to stay under budget, explaining the appearances of Blowfish, Weevils and Hoix, who can't possibly be major players. I'm not really bothered by the so-called allied races (Draconians, Judoon and potentially neo-Silurians) because all they need to do is believe the Doctor destroys the universe and they can get in on this alliance (almost literally with the devil). It might have been nice to see Jack/Torchwood there as well, regretfully putting the Doctor in a box.
Item 7: The Cybermen are problematic because they look like the alternate universe's Cybusmen, but have the classic Cybermen's ships (from The Invasion). They sometimes say "delete", but also talk about assimilation (stick it to those copycats, the Borg!). They have full skulls inside their helmets rather than naked brains, but here's also a mention of "all possible universes" as if they were the "void walkers". I postulate that the Cybusmen could have encountered our universe's Cybermen and joined forces with them, making both "races" stronger in the process. In any case, I was always disappointed with the Cybusmen because RTD essentially made them too much like robots. In no more than 10 minutes, Moffat made them scary again, returning to the body horror that was integral to their original conception. Except crazier. Like a scene out of The Thing. Major props.
Item 8: How did all those races get their ships Roman times? I say the Daleks created a time corridor they could all fly through. After all, it's highly doubtful they would share their time travel technology with all of them.
Item 9: "...off the wrist of a handsome time agent." I suppose the line is supposed to evoke Captain Jack, but it could just as well be John Hart. I'm thinking all the time agents have had work done, and this is just a coincidence lest I have to imagine major characters mutilated off screen. As for the vortex manipulator, it's most probably the Doctor's ticket out of the box. It's among the tools he's working with when River calls him from horseback. I'd put up a screenshot, but I promised to keep the spoiler pics to a strict minimum.
Item 10: There's a wonderful bit at the end when silence falls on the universe and the music drops out. I got a lovely frisson.
Item 11: And best of all, NO PREVIEWS. If it weren't for the "To be continued", parents could legitimately scare their kids into thinking that the Doctor's adventures are over. I love that Moffat's playing so close to the vest and can't wait to be surprised by The Big Bang, this coming Saturday!