The Fourth Dimention
The Cult of Skaro are Sec, Caan, Jast and Thay. Jast was originally called Rabe, but the production team changed their minds and renamed him during sound dubbing for the episode.
This is the first time the Daleks and Cybermen have battled each other on TV, although both briefly appeared during the Doctor's trial in the final episode of The War Games (1969) and in separate scenes during The Five Doctors (1983).
The final Bad Wolf Bay scenes were secretly filmed at a place called Southerndown, on the Welsh coast just west of Cardiff.
Time To Depart
This episode sees the first instance of a Dalek's ability to escape from a dangerous situation by using an Emergency Temporal Shift. This feature is almost certainly limited to The Cult Of Skaro.
Rose Tyler: Earth Defence
Russell T Davies briefly considered creating a one-off special starring Billie Piper, following Rose's adventures on the parallel Earth. He abandoned the idea, considering it a spin-off too far.
Catherine Tate's appearance, one of the best kept secrets in Doctor Who, was secretly filmed during the Series 2 wrap party.
The 3-D Doctors
Although the Doctor wears 3-D glasses in the episode, the only real use of 3-D filming on Doctor Who was the Children In Need special, Dimensions In Time (1993).
It was later revealed in the Torchwood episode Cyberwoman that Ianto Jones used to work at the Canary Wharf branch of Torchwood. Ianto's first actual appearance in Doctor Who was The Stolen Earth.