Doctor Who re-materialises on TV screens on Saturday with David Tennant cast as the tenth itinerant Time Lord.
The second series promises the return of some favourite baddies, as well as guest appearances by robot dog K9 and a former companion, Sarah-Jane Smith.
Billie Piper, who plays the doctor's current companion, Rose Tyler, said it also presented her with the challenge of bringing some comedy to the role.
She told BBC Radio Wales: "I was quite scared if the truth be told."
The laughs jostle with frights in the first episode which sees Piper's character, Rose, being taken over by a foe from the last series, the super vain Cassandra, played again by Zoe Wannamaker.
Piper said: "I was quite nervous about the being-possessed-by-Cassandra theme, because it was something that I've never really done before, and a lot of it was comedy that I hadn't really played before."
She said Rose was more "possessive and uptight" due to having once "lost" the doctor his regeneration and the appearance of Elisabeth Sladen, the doctor's former companion.
She said: "She is a bit feistier this time round and very jealous, which I love playing.
"She feels that at any given moment he can be taken away from her. And I don't think she ever considered that before.
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"She could contemplate monsters and all of that, and dealing with alien life forms and parallel worlds, etc, but the idea of losing the man she loves is really shocking and sad. She doesn't want it to happen again.
"She reacts terribly to meeting Sarah-Jane. That's when the jealous streak starts to kick in, out of fear that she's not his greatest companion and that he's had millions of them before.
"It's like meeting the ex-girlfriend, and we have this wonderful bitch fight which is worth watching."
Piper added that she feels at home in Cardiff now, after being based in the city for two seasons of the sci-fi drama.
She said: "I've been here for almost two years now, I'm native. I'm Welsh and I've learnt some Welsh words this year - none of which I can tell you because they're all rude - but I love it here.
"I think I've met some friends for life."
Doctor Who is screened at 1915 BST on Saturday on BBC1