River and the Doctor are in danger of being sacrificed to the rain gods in this Neil Gaiman-scripted Doctor Who minisode. Naturally the Doctor has an escape plan—though it's not necessarily an elegant one.
Over on his Tumblr, Gaiman explains that this started as a deleted sequence from the episode "The Doctor's Wife," and was then drawn by Mark Buckingham as a three-page comic. Gaiman then rewrote the scene as a minisode, titled "Rain Gods," featuring River and the Doctor for the Series 7 box set.
Edit: A couple of folks have noted that the credits say "by Steven Moffat." On Tumblr, Gaiman says that credit is erroneous.