In one scene, someone asks Aria her name but cannot hear her answer because of a noise, so she writes it on the fogged window of the train, then subsequently goes missing. These plot points are all from the Hitchcock film The Lady Vanishes.
Spencer wears a Marie costume and Toby wears a Harry costume. Before Toby walks away, Spencer says, "If you need me, whistle. You know how to whistle, don't you?"