 The episode featured an ensemble of family and friends of Gwen and Rhys previously unseen in the series . William Thomas and Sharon Morgan were cast as Gwen 's parents Geraint and Mary Cooper . Davies re @-@ introduced the characters during the fourth series of the show , considering Thomas and Morgan to be " two fine Welsh actors " . Thomas had previously appeared as two different characters in the 1988 Doctor Who serial Remembrance of the <unk> and the 2005 Doctor Who episode " Boom Town " . Upon appearing in " Something Borrowed " he became the first actor to have appeared in all three of the classic series , new series and Torchwood . Nerys Hughes played Rhys ' mother Brenda Williams , in addition to a duplicate form of the alien Nostrovite . Like Thomas she had previously appeared in a Doctor Who serial ( the 1982 story Kinda ) . Hughes enjoyed getting to play a " monster " for the first time in her career which involved having " fangs and claws and red eyes " and being <unk> up so " all this black blood can <unk> out when I get shot " . Despite the funny aspect of the script Hughes took the role seriously stating that " everyone plays it for real " and that " you can 't camp it up " . She believed that as an actor " you 've got to believe what you 're doing " . 
