Without Russell T Davies, it is unlikely that Doctor Who would've ever returned to our screens, and he certainly wrote some fantastic episodes and characters that drew in new and old audiences alike. Departing the show in 2010 along with David Tennant, it has now been over a decade since his time on the show came to an end.
Yet it would seem that his era of the show is still one of the most popular.
Discuss Doctor Who with a more casual fan and they'll almost definitely tell you that their favourite period of the show was when David Tennant was The Doctor. This is sure to be in part due to Tennant's fantastic performance, however it would be criminal to ignore Davies' contributions, namely the new monsters and alien races he introduced.
In fact some of the most memorable monsters from the show's lifetime originate from series one to four, and are yet to return.
While Doctor Who should always strive to introduce new and interesting threats, there is nothing wrong with bringing back a few old favourites. But that doesn't mean just bring any monster back for the sake of it. Sometimes a monster is best left as a standalone appearance. Many argue that The Weeping Angels have lost their original charm due to their constant reappearances, so when bringing back a race of aliens, it has to be done with care.