The shot of the man covered in pigeons at Washington Square Park was filmed by Chris Columbus during a set visit.
Sian Heder got the idea for the film when she was working as a nanny when she first moved to L.A.
This film is a feature-length evolution of Sian Heder's 2006 short, Mother (2006). In fact, the the script for Mother is re-used almost word-for-word in the sequence where Tallulah first encounters Madison and her mother in the hotel suite.
During the subway scene there's an ad for an upcoming game of soccer of the Copa America between Chile and Perú, that sets the date of the movie around Jun 29, 2015. The security camera footage from the elevator shows Jun 8, 2015.
In Juno (2007), if the baby that Elliot Page's character was expecting were a girl she would be named Madison by the adoptive mother. Also, Allison Janney played Juno's stepmother in the same movie.