In all seriousness, the weeping angels are aliens who appear to be stone statues until you stop looking at them. If you stop looking at them (or even blink) they will attack. They do not kill you, but instead send you back in time and feed off the temporal energy from your unlived life. As a side note, I believe that they will play an integral part in the 50th anniversary. There have been many hints that my favorite villain, Omega, has been pulling the strings for the past several years and will make his return for the milestone series. The last time the Doctor faced Omega in “Arc of Infinity,” there was an accident which involved a stone angel, which I believe is the origin of the creatures.
The Doctor, Amy, and Rory start off enjoying a quiet afternoon in Central Park as the Doctor reads aloud from a detective book he has found. The serene setting is quickly disturbed as Rory wanders off to get coffee and suddenly appears in the Doctor's book. The angels have zapped him back to 1938, where he discovers that the protagonist of said book is none other than his daughter, River Song.
When the title of this episode was first announced, I felt it was fairly obvious which Manhattan landmark would be integral to this story, but still enjoyed its reveal immensely. For the sake of those who did not come to the same conclusion as I did, I will not spoil the surprise.
This time around, the angels have learned a new trick—instead of just dropping off people to any random time, they have become organized. By keeping them all in a derelict hotel, they have built a farm where they can continually feed off people's potential lives until they die of old age.
Steven Moffat is back again at the top of his game. He has written an emotional send-off for our companions that leaves the audience in suspense throughout the entire episode. For a while now, I have felt that the pair of companions have reached the extent of their story. They had a great ending, and I look forward to a new companion joining the show.