There can't be too many young actresses that would turn down the chance to whizz through time fighting a sc-fi war as the Doctor's assistant.
Freema Agyeman plays Martha Jones
For one 28-year-old, the dream has become a reality.
Freem Agyeman is just about to make her first appearance as Doctor Who's new assistant Martha Jones.
The new series starts on Saturday, and Freema's character will come face-to-face with the time lord - on the moon.
Freema's well aware of the pressure she'll be under to fill Billie Piper's shoes as the last assistant, Rose Tyler.
Television fans may well recognise Freema from The Bill, and playing Lola Wise in the now-defunct Crossroads.
Watch Freema on Breakfast via the link to the right of this page
Doctor Who, 7.00pm, BBC One, Saturday