Sinead Keenan, an Irish actress who has been active in British TV for several years, played Addams in the Doctor Who television story The End of Time. She also voiced Margery Phipps in the Big Finish Doctor Who audio story Council of War, Aoife Dineen in Iterations of I, Stephanie Wilton in The Reesinger Process, Rosheen in The Highest Science and Mary Summersby in The Darkness of Glass.
She is the elder sister of Rory Keenan.
Russell T Davies wrote in The Writer's Tale that he had written Addams as Sinead Keenan, who is an inspiration to him.