#9 - "Last Christmas" (2014)
For once, Santa (Nick Frost) isn’t a robot in theDoctor Who
Christmas installment. He's the real flesh and blood thing. Sort of. He comes to the Doctor and Clara in a reverie caused by Dream Crabs, monsters who feed on human brains.
The man behind Strax (Dan Starkey) appeared as one of Santa's elves, and one of Patrick Troughton's (the Second Doctor) sons played Professor Albert Smithe.
Jenna Coleman (Clara Oswald) almost left at the end of of Season 8 but chose to stay on, so Moffat rewrote the ending with Clara as an older woman.