Moffat talks about the search for an actor to replace Matt Smith on the BBC One sci-fi drama, in an interview shot at Comic Con 2013 in San Diego.
The showrunner also reveals whether or not he would consider casting an older Doctor, and which fan favourite characters will be continuing into the 12th Doctor's era.
"You can push [the 12th] Doctor a bit further maybe, if you've got a familiar world around him," he hinted.
The first full series featuring Smith's successor will air on BBC One in 2014, with Moffat giving DS an update on the current status of series eight.
Doctor Who returns to our screens for its 50th anniversary special on Saturday, November 23.
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Comic Con 2013's Best Costumes - in pictures: