Like Earthshock it was notable for clever secrecy in its marketing. Most 2008 purchasers had no idea that the story involved Adric at all, thanks to his listing in the credits as the "Scorpion King", and the fact that the character was played here by Andrew Sachs, not Matthew Waterhouse. Though Brewster did not appear until the closing minutes of the story, Boy was important to the development of that character by highlighting important similarities with Adric, and for being the adventure in which Brewster was formally invited to join the TARDIS crew.