The Sontaran Stratagem wasn't too bad at all. In hindsight, the plot was a bit rubbish, but there were lots of other good bits to make up for it; Donna's reunion with her family was surprisingly touching, and the Sontarans themselves were quite brilliant, coming across as outer space versions of the stereotypical blustering English colonel. It's always good to see Martha return, too.
Not much on the way of "code words" this week. Aside from a nod back to the Time War, with the Sontarans miffed that they weren't invited, the most notable nugget was a reference to the "15th broken moon of the Medusa Cascade".