Matt Smith has revealed plans to adapt his Doctor Who role into an evil Breaking Bad-type character before he left the show.
The actor, who starred as the Doctor from 2010 to 2014, said writer Steven Moffat wanted to explore the darker side of the character had Smith decided to stay with the BBC One sci-fi series.
Appearing at New York Comic Con, Smith said: "I was really interested in that element of the Doctor.
"I think if I'd carried on that was what Steven was going to explore. It would have been like Breaking Bad.
"You've got to be really careful with him as a character. It would be hard to watch him be really awful to everyone."
The award-winning US drama Breaking Bad starred Bryan Cranston as Walter White, a terminally-ill chemistry teacher who becomes a drug kingpin.
Smith appeared on a panel at New York Comic Con alongside his former cast-mates Jenna Coleman, who played Clara Oswald on Doctor Who, and Alex Kingston, who plays River Song.
Kingston defended Smith's decision to leave the show in 2014, when he was replaced by current Doctor Who star Peter Capaldi.
She said: "The truth is there is only a certain amount of time that anyone can play the Doctor because you get burnt out.
"The actors who play the Doctor are worked so hard. If you think about it: they have these reams and reams of dialogue that mostly make no sense at all.
"There's a point where... you're going to burn out. It's a shame when they go but at the same time, for their own health, they have to stop."
New York Comic Con runs until Sunday.