Commander Strax - everyone's idea of the ideal Sontaran - is proving to be a major hit with viewers of 'Dr Who'. When the Sontarans first appeared they were far uglier and had a repulsive greenish/brown skin and a 'scratchy' voice quality that was not to everyone's liking.
However, since Dan Starkey has taken over the role, we now see what a good actor can do with it! Starkey is belligerent, funny, loyal and everything you need in a team member, providing you don't mind finding your house defended by a moat filled with acid and 'splitter mines', that is. Matt Smith freely admits that he tries to base his scenes with Strax on those between Edmund Blackadder and Baldrick; and I must say that you can get a sense of that (the scene with the Memory Worm in the cab, plays out just like a 'Blackadder' episode).
Brought back to life after the battle at Demon's Run, Strax joins Madam Vastra and her wife, Jenny, in Victorian London, acting as their butler (which makes him one of the strangest butlers, ever!) Since they live on Paternoster Row, they are sometimes known as the Paternoster Gang, and they take great pride in dealing with the run-of-the-mill Victorian criminal element and any aliens that come their way.
These three characters - supplemented by the Doctor, from time to time - work SO well together, that there have been serious calls for a 'spin off'. After all, the BBC has a track record of producing the very best in Victorian drama, and they have an enormous database of locations, props and other items to support such a venture.
At this moment, Stephen Moffat is resisting all calls for a spin off, saying he hasn't the time....but we have to be like water on a stone, and wear him down!