Sally and Larry have the book/DVD shop, "and nothing more", Sally insists, between them. Until after they meet the Doctor, who's carrying a bow and arrow. Who else carries a bow and arrow and causes a Relationship Upgrade... and is often mistaken for an angel?
Why do the Angels take so long to get from point A to point B despite being "faster than you can believe"? Because animals and insects are living beings, too and whenever they look at the Angels, the Angels have to stop just like they would for a human.
When Sally and the Doctor are communicating via the DVD conversation, the Doctor reaches the end of the transcript shortly after Sally tells Larry (who is writing down her side of the conversation) to not take his eyes off the Angel, meaning he can't see to write any more of her side of the script.
Better yet, Ten presumably knows from Sally's later notes how she and Larry escaped the house, but he's obliged to stick to the transcript and keep acting like he doesn't know. Not least, because he knows that tampering with the Stable Time Loop or even reassuring them that they'll get away might change history, making them slow enough for the Angels to catch...
Also, the four angels all conveniently standing within each other's eyesight when the TARDIS leaves without them makes the Doctor look very lucky to have planned that in advance. But it's entirely possible that the folder Sally gives him also has a note on what happened, meaning that he would know in advance not to instruct them on how to use the TARDIS without it leaving them behind.
Cathy's grandson, with his short red hair and black suit, looks a lot like classic-Who companion Turlough. This could be a deliberate Easter Egg for old-time fans ... and one that makes his arrival even more suspicious to viewers who remember that character, who'd first joined the Doctor's ensemble as the Black Guardian's unwilling agent tasked to murder Five.
He's also very nervy and jumpy, which at first only adds to the viewer's suspicion of him...until we learn the full truth of what happened to Kathy and his promise to her. She likely warned her grandson that the house was dangerous, in order to make sure what happened to her didn't repeat with him, and he's clearly eager to get in, deliver the letter and get out again as soon as possible.
Weeping Angels can project themselves through images. Sally gives the Doctor a folder containing a photo of an Angel. In the Doctor's timeline, this is before he and Martha get sent back to The '60s. Maybe the Angel from that photo was the one that sent them back in the first place.
At first it doesn't make sense that Wester Drumlins is still attached to the National Grid (which allows for the final climactic scene in the cellar) after being abandoned for so many years, but it's likely that someone in the past (probably Billy) arranged for the electricity to be kept on, since they knew it was crucial for the time loop.
What if someone turns out the lights (or the light bulb dies, or power goes out, or...) in that cellar after the end? Better hope that Angels can see in the dark... What if something falls in their vision, like debris? Or if they get so dusty their vision is obscured?
The Lonely Assassins game shows what happened to the Angels. Someone bought Wester Drumlins and disturbed the statues.
Hopefully the Doctor also has a plan to deal with them more permanently, now that all four are simultaneously paralyzed and he has the TARDIS's resources to draw upon. He'd have had plenty of time to devise one while he and Martha were stranded; he just couldn't put it into motion until after Sally'd received his messages, trapped the Angels, and sent his ride back to them.
Of course Angels can see in the dark, why else would they turn out the lights while attacking to blind their victims?
It wouldn't even be that hard—materialize the TARDIS around the angels, then dump them in a black hole, or put all of Wester Drumlins in a time loop so that nobody else could enter going forward.
As revealed in "The Time of Angels", Whatever takes the image of an Angel becomes itself an Angel; and with it being one of the most popular episodes, there's a lot of DVDs of the episode...
The nature of the Stable Time Loop means that Billy Shipton has to spend 38 years knowing exactly the day he is going to die. That can't have been easy on him.
On other other hand, knowing that you're going to live to a ripe old age could be a comfort in some ways. And knowing exactly when you're going to die means you can be sure you'll get all your affairs in order.
This episode was made in 2007. The video store isn't likely to stay in business long. (Then again, bookshops are still going relatively strong...)
Why, at the beginning of the episode, does one of the Angels chuck a rock at Sally's head, rather than the old reliable method of sneaking up on her and sending her back in time?
Why don't the heroes just blink one eye at a time when having staring contests with the Angels? Probably just that it would look really silly.
Moreover, doing so would require great concentration, which is not very helpful if one is also trying to be alert to whether any of the other three Angels are nearby while you're keeping the one you're looking at pinned.
Amy does in fact blink one eye at a time in when she meets the Angels in Season 5.
Recent studies suggest that blinking doesn't just moisten and clean your eyeballs: it gives the brain's attention and visual centers a brief, but necessary pause from active input while their neurons "reboot". Not blinking is therefore mentally exhausting and would inevitably cause the onlooker's attention to slip. And no, winking alternate eyes wouldn't make up for this, because only involuntary blinks count.
Why did Larry's transcript of the Doctor's lines include conveniently wide spaces to write in Sally's lines?
Because he's mentioned earlier:
"It's like we're hearing half a conversation. Me and the guys are always trying to work out the other half."
Sally watches one of the Doctor's videos, with Larry making a transcript of her side of the conversation which the Doctor will "later" use when recording the video. This gives her all the information she needs to return the TARDIS to him. So what's on the other sixteen videos?
Probably the same Easter egg. It's on seventeen DVDs because they are all owned by Sally, which is how she knows that the message is meant for her.
If Angels turn to stone whenever they're being watched by "any other living creature", what about the hundreds of insects that must be looking at them at any given moment?
Possibly it requires some level of sentient understanding of what is being observed, so only sentient beings can paralyze them?
Insect vision is very different to mammalian, so unless the insects are swarming around the Angel, they probably wouldn't see it at all. It's also never explained how much of an Angel you have to see in order for it to turn to stone.
When meeting up to view the DVD and the Easter egg of the Doctor, why do Sally and Larry go back to the creepy house where several people have already disappeared, and which seems to be a base of operations for the monsters hunting her, as opposed to going somewhere with plenty of witnesses?
