An unexpected cameo by Billie Piper in the opening episode of Doctor Who's fourth season surprised viewers of the show.

Piper reprised her role as Rose Tyler for a brief scene with current companion Donna Noble, played by Catherine Tate. The moment was not featured in the cut shown to journalists at last week's press launch and Piper's name was not listed in the cast lists in any listings magazines, which successfully prevented the news from leaking.

The appearance was Piper's first on the show since the second season finale 'Doomsday' in 2006, in which Rose was trapped in a parallel universe and separated from The Doctor.

On BBC Three's Doctor Who Confidential, Russell T Davies joked about the cryptic nature of the scene: "What's going on there? How could she be standing on that street? Why did she fade away? Like I'm going to tell you now! You've just got to keep watching."

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