After Claire discovers who Peyton really is, her husband calls the police. He reports the address as "808 Yakima". This is the actual street address of the house in which most of the movie was filmed.
The musical theme that is featured in the opening credits, that Payton hums when strolling the baby through the park, and that Michael hears on the radio at the climax is "Poor Wandering One", from the William S. Gilbert and Arthur Sullivan musical "The Pirates of Penzance".
The title of the film is taken from the poem of the same name written by William Ross Wallace. The poem praises motherhood as the primary impetus for changing the world.
Rebecca De Mornay had actually been angling for the part of Tinkerbell in Hook (1991). Losing the role to Julia Roberts prompted her to actively seek something a little darker instead.
Sir Arthur Sullivan is cited on more occasions throughout the movie. Already mentioned: Peyton humming music of the "Pirates of Penzance" and the music at the title credits is based on the "Pirates of Penzance". But also, Michael and Emma are singing Sullivan's "HMS Pinafore" in the bathroom at the beginning of the movie; the clock radio in the basement plays more music of the "Pirates of Penzance"; in the house, a poster of Sullivan's "HMS Pinafore" can be seen on the wall.
Kevin Spacey was considered for the role of Michael Bartell.