This episode marks the return of Jenna @-@ Louise Coleman , who previously appeared in the series opener , " Asylum of the Daleks " . Coleman was cast because of her chemistry with Matt Smith , and especially because she was able to talk faster than him . She auditioned for the role of Clara , not Oswin from " Asylum " , as the concept of the two characters being the same only occurred to Moffat whilst casting for Clara . The production team requested that the press and fans who attended advanced screenings keep Coleman 's appearance a secret until " Asylum " was broadcast ; the effort was ultimately successful . Moffat stated that the introduction of a new companion made " the show feel different " and brought the story to " a new beginning " with a different person meeting the Doctor . Smith said that Clara was different from her predecessor Amy Pond ( Karen Gillan ) , which allowed the audience to see a different side of the Doctor . Coleman described her as resourceful and not intimidated , citing the reason for following the Doctor at the beginning as pursuing answers . The Clara who would become a travelling companion of the Doctor would not debut until the Spring premiere , " The Bells of Saint John " ; save for a brief cameo at the end of " The Snowmen " . Coleman stated that she played each version as individuals with " trust that there would be a payoff " to her mystery .