Toby Whithouse originally conceived the show as a drama in the vein of This Life (1996) with the three characters sharing a flat. Originally, Mitchell was a sex addict, George had anger-management problems and Annie was an agoraphobe. Whithouse added the supernatural elements later, finding what he believed to be the underworld equivalent for each character: the sex addict Mitchell became a vampire, the angry man George became a werewolf, and the agoraphobe Annie became a ghost.
The producers of the show felt that it would stretch the budget to the limit if they had to digitally remove Aidan Turner's reflection from everything that had a reflective surface, so they came up with the notion that vampires can only be invisible in objects with silver backings, such as mirrors and cameras.
According to Aidan Turner in a BBC3 question-and-answer session, Mitchell's fingerless gloves were more necessity than fashion statement due to the freezing set temperatures filming in wintertime Bristol.