Jenna-Louise Coleman's portrayal of two characters in 'Doctor Who' is part of writer Steven Moffat's "genius plan".
The 26-year-old actress made an appearance in episode 'Asylum of the Daleks' in September, where she played deceased Dalek Oswin Oswald, but she says it wasn't the initial plan as she was supposed to make her debut as the Time Lord's new sidekick Clara Oswin in this year's Christmas special episode, 'Doctor Who - The Snowmen'.
Speaking to Entertainment Weekly, she explained: "It's interesting actually - I think I can tell you this - that that was never the initial plan either, to have me be Oswin.
"That was part of a genius plan that Steven came up with halfway through the audition process. That was already written but not written for what was to be the new companion.
"I was auditioning for the companion and then I got all these sides and I was like, 'Who's Oswin? They clearly don't know what they want, they obviously don't know what they're looking for. They just want people to show them different things and see.' This is what I assumed when I was auditioning, not realising that it's basically Steven's mad genius again."
Jenna admits it is tough to speak about Clara because she is a mystery to both the viewers and characters in the show as no one knows who or what she is.
She added: "That's why it's so difficult [to talk about]. Because of the way it started with Oswin, it's really difficult to say much: Where she's from, what period she's from, what planet she's from, even."
'Doctor Who - The Snowmen' Christmas special will air on Christmas Day (25.12.12) on BBC One.