Lord Peter greets Bunter with "Ah, Bunter, you come most carefully upon your hour." He is quoting Francisco in Act 1, Scene 1 of Shakespeare's Hamlet.
The song indicated as Spanish Harlem is actually an old folk song called La Paloma which was written in 1860, so it is not an anachronism as indicated in the original post. The two songs/melodies have a similar rhythm, but different melodies.