P.S. was a short animated coda to the events of The Angels Take Manhattan.
According to writer Chris Chibnall, it was originally intended to be a live-action DVD extra, but actor unavailability meant it couldn't be filmed, so instead its storyboards were animated and narration was commissioned from Arthur Darvill. Ultimately the scene was released as a webcast by the BBC following the broadcast of The Angels Take Manhattan.
Narratively, this scene is meant to give Rory Williams's character closure, and by extension, show that he and his wife Amy Pond would live out a happy life in 20th century New York City. It also technically serves as Darvill's final regular performance as Rory.
The Doctor leaves with Amy and Rory after having dinner with them and Brian. A week later Brian answers a knock at the door. An American man stands there; he passes Brian a letter and walks in. Brian sits in the lounge and reads the letter. It is from Rory, and it says that he and Amy were permanently trapped in the past in New York City. However, Rory assures his father that they lived happily together for the rest of their lives, and in 1946 they adopted a son named Anthony, who is the man that delivered the letter. Rory also tells Brian that he misses him and loves him, and he understands how weird it must be to have a grandson who is older than he is. Brian goes into the hall to see Anthony, who offers a handshake. Brian hugs him instead.
Home video release Edit
To date, no home video release has occurred, with P.S. being omitted from both the UK and North American editions of the Series 7 DVD and Blu-ray box set.