ri et ▁Jones ▁is ▁regularly ▁told ▁this ▁after ▁introdu cing ▁herself , ▁multiple ▁times ▁in ▁both ▁" The ▁Christmas ▁In vas ion " ▁( 2 0 0 5 ), ▁and ▁in ▁" The ▁St olen ▁Earth " ▁( 2 0 0 8 ). ▁ ▁The ▁Doctor ▁suggests ▁that ▁Os good ▁is ▁a ▁hy brid ▁between ▁a ▁Z ygon ▁and ▁human , ▁continu ing ▁the ▁theme ▁of ▁hy br ids ▁mentioned ▁in ▁" The ▁Mag ician ' s ▁App rent ice " ▁/ ▁" The ▁W itch ' s ▁Famil iar ", ▁" The ▁Girl ▁Who ▁D ied " ▁and ▁" The ▁Woman ▁Who ▁L ived ". ▁ ▁Out side ▁references ▁The ▁Doctor ▁plays ▁the ▁opening ▁to ▁the ▁h ymn ▁" A maz ing ▁Grace " ▁on ▁his ▁electric ▁guitar . ▁ ▁Clara ▁claims ▁to ▁memor ize ▁obsc ure ▁facts ▁to ▁help ▁her ▁win ▁at ▁T rivial ▁P urs uit , ▁a ▁popular ▁t riv ia ▁qu iz ▁board ▁game . ▁She ▁also ▁explains , ▁from ▁her ▁knowledge ▁of ▁T rivial ▁P urs uit , ▁how ▁the ▁town ▁of ▁Tr uth ▁or ▁Con sequ ences ▁got ▁its ▁name ▁from ▁the ▁television ▁show ▁Tr uth ▁or ▁Con sequ ences . ▁ ▁As ▁well ▁as ▁ident ifying ▁himself ▁as ▁" Dr . ▁Dis co ", ▁the ▁Doctor ▁also ▁calls ▁himself ▁" Dr . ▁Fun ken stein " ▁after ▁a ▁song ▁of ▁the ▁same ▁name ▁by ▁the ▁band ▁Parliament . ▁ ▁Broadcast ▁and ▁reception ▁The ▁episode ▁was ▁watched ▁by ▁ 3 . 8 7 ▁million ▁view ers