Batman
Christopher Nolan is worried that any sequel to Batman Begins and The Dark Knight may not be as good as his previous movies.
Both the movies in the revitalised Batman franchise have been a critical and commercial success and since the release of The Dark Knight speculation has grown as to what path the movies would take and if there would be a sequel at all.
Talking to USA Today filmmaker Nolan said: "I don't know why they're hard to do. Maybe there's so much expectation to them. I wouldn't want to do one if it weren't going to be as good as the first or second. That's not respectful to the fans.
"It was obvious when the box office was so big that we had underestimated how ready fans were to reboot the franchise," he said. "The worst thing you could do now that you've gotten the plane back in the air is mess up the landing."
The Dark Knight was the biggest grossing movie of 2008 grossing just shy of the $1 billion mark, however it's re-release in the new year may see it surpass that barrier and join Titanic, The Lord of the Rings: Return of the King and Pirate of the Caribbean: Dead Man's Chest as only the fourth movie to do so.
Further hype surrounded the film after the untimely death of actor Heath Ledger who plays the Joker in the new film. Ever since it's release there have been suggestions that Ledger, and possibly the film itself, may find itself amongst the contenders come Oscar time.