Some conflicting reports have appeared online and in printed newspapers that Christopher Eccleston (The 9th Doctor) agreed to appear in the 50th Anniversary Special, and then pulled out.
The rumours, which were unsurprisingly started by The Daily Star newspaper, claimed Eccleston was all set to star in the special but as filming started, he apparently pulled out.
An official BBC source (speaking to Digital Spy) has reportedly claimed that: “Eccleston was never attached to the 50th and the decision has had no impact on production.” The source was further quoted as saying the following:
“Chris met with Steven Moffat a couple of times to talk about Steven’s plans for the Doctor Who 50th anniversary episode. After careful thought, Chris decided not to be in the episode. He wishes the team all the best.”
Further rumours claim that Paul McGann has stepped in and the storyline originally intended for The 9th Doctor has simply been swapped for The 8th Doctor.