9. Doctor Who's Adorable Barmaid
As he travels to Dracula's castle in the first episode, Jonathan Harker reads a letter from his fiancée Mina (one of several times that the show references the book's structure as an epistolary novel, built around letters and diaries). In her letter, Mina flirtily declares herself fine with the potential of Jonathan being tempted by the local women as she can comfort herself with Edwin from the office, the butcher's boy, or "the adorable barmaid at the Rose and Crown, who I know you have also admired."
Obviously the Rose and Crown is a fairly standard English pub name that doesn't have any particular relevance to the Dracula story. It does, however, ring a bell for fans of Moffat's previous work, who are already well familiar with an adorable barmaid at the Rose and Crown.
In the Moffat-penned 2012 Christmas special of Doctor Who, Matt Smith's Doctor travels back to Dracula's 1890s setting to encounter the Victorian version of Clara working as, yes, the barmaid at the Rose and Crown.
The same Dracula episode, meanwhile, also contains what may be a nod to Gatiss and Moffat's previous series when Sister Agatha mentions finding Mina through "a detective acquaintance in London."
While Dracula has cropped up as both a fictional character and a real vampire in Doctor Who's extended universe of novels and comics, there has never been an onscreen clash between the two. Could this throwaway reference be setting that up? Probably not, but it's still a nod that fans of both will have enjoyed.