When the Doctor pulls Clara out of the decontamination chamber his right hand switches from holding her waist to patting her cheek between shots.
The Sweetville residents sing Parry's Jerusalem; the story is set in 1893, but Parry didn't write the music until 1916.
Mrs Gillyflower sings the final lines from the Percy Dearmer 1906 setting of "To Be a Pilgrim", singing Monks Gate - the tune set by Vaughan Williams for the New English Hymnal. The NEH first appeared 13 years after the episode is set.