Karen Gillan
From Tardis Wiki, the free Doctor Who reference
Karen Gillan is a Scottish actor, she acted the Soothsayer in The Fires of Pompeii, and will play the first companion of the Eleventh Doctor, Matt Smith, in Series 5.
Gillan's appointment to the series was announced on the 29 May 2009 by the BBC.[1]
She is one of only a handful of actors to return to the series as a companion after having previously appeared in a different role. Others have included Peter Purves, Ian Marter,Freema Agyeman and Ian Marter.
