gun and shoots at the suit. However, she realises too late that the helmet's visor has opened to reveal the little girl. Continuity The TARDIS had been previously turned invisible by damage to its visual stabiliser in the Second Doctor story The Invasion (1968). When Canton first leaves the TARDIS, the Doctor remarks, "Brave heart, Canton," a reference to the Fifth Doctor's recurrent statement to his companion Tegan Jovanka, "Brave heart, Tegan." When Amy asks the younger Doctor to trust her, he asks her to swear to him on something that matters. After some thought, she smiles and says "Fish fingers and custard," referring to events in "The Eleventh Hour," when Amy first meets the Doctor as a little girl. Production Writing The episode was written by Steven Moffat, who took charge of the show in 2010. Moffat wanted the 2011 season to start with a two-part story in an attempt to begin with more gravity and a wider scope in plot, as well as wanting the episodes to be one of the darker ones in the series. "The Impossible Astronaut" / "Day of the Moon" was the first two-part episode to open a series since the 1985 Sixth Doctor story Attack of the Cybermen. In the Doctor Who Confidential episode following the broadcast of "The Impossible Astronaut," Moffat stated that in his view, it was one of the darker episodes of the series, but still maintained the same level of humour. The inclusion of the Doctor's death felt like a series ender for some of the producers, but was actually there to "kick it off." In writing the death scene of the older version of the Doctor, Moffat wanted to acknowledge to the audience that Time Lords are not invincible, and could still die permanently if killed before regeneration. In creating the Silence, the alien antagonists of the episode, Moffat wanted them to challenge past monsters in terms of "scariness." He felt these creatures are a "much bigger deal." The aliens' design was partially inspired by the figure from the Edvard Munch painting The Scream. Casting In October 2010, it was announced that Mark Sheppard, who had appeared in other science fiction series including Battlestar Galactica, Firefly, Supernatural, and Warehouse 13, would make a guest appearance on Doctor Who. Sheppard described playing Canton as a "dream job," and said he wished to appear in another of Moffat's works, including