Along with the story's second half, "Journey's End" (4.13), this episode has the largest opening-title cast listing of the modern series: six names (Tennant, Tate, Agyeman, Barrowman, Sladen and Piper) appear before the title, rather than the usual two... in the same amount of time.
In giant 3D text not too dissimilar to the opening credits: "TO BE CONTINUED"