Spoilers!

I apologize if you’re here and don’t want to be spoiled for the finale of David Tennant’s run on Doctor Who. I advise not reading any further…

The rumors of Billie returning have been circulating for months and now there is proof of her appearance in the Finale special! The Daily Mail has the pictures and the news:

Their on-screen pairing as Rose and The Doctor made both Billie Piper and David Tennant household names.
So it was only fitting that new mother Billie should return to Doctor Who for Tennant ’s final two episodes as the Timelord. The 26-year-old actress joins an all-star cast for the emotional send-off of the popular star.
Yesterday Tennant, dressed in the Doctor’s signature suited style, was seen filming some of his last scenes from the sci-fi family drama.
He clutched the wall in apparent distress as he walked through air swirling with snow in a Cardiff Street. Billie had earlier filmed scenes nearby, wrapped in scraf and gloves, and the two were seen chatting together in a break from filming.
The final two episodes will be broadcast over the Christmas period and will see Tennant regenerate as Matt Smith, who replaces him as the 11th Doctor.
It will also be the last of Russell T Davies’ four 2009 specials and signals the end of his five years as head writer.