A clip of the 2006 Doctor Who Christmas special - The Runaway Bride - has been leaked on the internet.
Four minutes of the show have appeared on the video sharing site YouTube, which lets people put video online for others to watch.
The clip shows the bride of the show's title trapped in a taxi, driven by someone dressed as Father Christmas.
It also shows the Tardis chasing the taxi down a motorway, bouncing off the road at high speed.
It's thought the clip comes from a special concert for Children in Need in Cardiff, where parts of the show were screened.
At that concert a live orchestra played some of the music from the show.
People working on Doctor Who didn't want to say anything about the leaked clip when they spoke to Newsround.