Steven Moffat said writing Doctor Who was "not a real job"
Steven Moffat has told Doctor Who fans to expect "new monsters" when he becomes the show's executive producer and lead writer.
Moffat, who is replacing executive producer Russell T Davies, was speaking at arts and comic book convention Comic-Con in California.
He told fans not to expect too many appearances from old characters.
"We're not in the business of being nostalgic, we're making nostalgia for the future, new monsters, new friends."
He was responding to their questions about the possibility of guest appearances from old characters - such as ex-Doctor Who companion Sarah Jane Smith, played by Elisabeth Sladen in the 1970s - as well as old enemies.
He told the San Diego convention: "Doctor Who is at its best when it's brand new and you've always got to remember that there's a new bunch of eight-year-olds watching every year and it has to be original - it has to belong to them."
But he said continuity when old characters did return was not difficult to achieve.
"Having taken the precaution of having memorised every single event in Doctor Who's history, it's fairly easy for me to keep continuity because I remember it all.
"In the end, a television series which embraces both the ideas of parallel universe and the concept of changing time can't have a continuity error - it can't.
"It's impossible for Doctor Who to get it wrong because we can just say 'he changed time, it's a time warp, it happens'."
Moffat has already written some of the most memorable Doctor Who episodes of recent times including Blink , of series three - which featured terrifying weeping angels - for which he picked up the best writer Bafta earlier this year.
Asked about his reputation for writing scary episodes he said: "If people are worried that because I'm taking over Doctor Who it's going to be just really, really frightening, if that's your concern thenů tough."
He also spoke to fans for the first time about getting the job he has "always wanted".
The writer said the prospect of taking over from Davies for the fifth series - due to be shown on BBC One in spring 2010 - was "just exciting". It was announced he was taking the job in May.
"I suppose it should be daunting or nerve-wracking but it's not a real job like working in a hospital - it's just fun."
He added: "I mean it's hard work too but most things that are fun are hard work."
Davies will be responsible for the specials shown in 2009
Last week, Moffat denied a newspaper report that he "quit" a deal to work on Steven Spielberg's forthcoming Tintin trilogy because of the doctor Who job.
A newspaper report that he had "turned down" a two-film deal with Spielberg was "a bit misleading", he told the BBC News website.
He had planned to finish Tintin before starting Doctor Who but was delayed by the US writers' strike, he added.
Davies will remain in charge of four specials to be shown in 2009.