This was only the second announcement of a new Doctor since Twitter was created, and the first since 2009 (not counting the announcement of John Hurt appearing in the 50th anniversary special!) so Whovians flocked to Twitter to discuss it.
When official Twitter account @BBCDoctorWho announced that Peter Capaldi would be the new Doctor, replacing outgoing Matt Smith, it was no surprise to see that Tweet get more than 30,000 retweets and favourites:
For the whole of Sunday, #DoctorWho trended in the UK as fans awaited the excitement. Hashtags on Twitter allow fans of anything - a TV show, a sports team or music fans - to congregate around the same conversation.
Steven Moffat trended number 1 in the UK and worldwide, David Tennant trended at number 3 worldwide, and at one point 7 of the ten UK’s trends were Doctor Who-related.
The BBC’s live coverage of the announcement started at 7pm UK time. The peak of Twitter conversation came at 7.27pm UK time, when the new Doctor was announced, with 16,198 tweets per minute (TPM). And celebrity Doctor Who fans and actors were also quick to get involved in the global conversation."
Source: Twitter YK's blog, 5th August 2013