The line, "The devil's greatest trick was convincing man that he didn't exist," is reminiscent of a similar line in another movie of the same genre, End of Days - Nacht ohne morgen (1999), in which Father Kotak (Rod Steiger) says: "Satan's greatest trick was convincing man that he didn't exist". It is also similar to Die üblichen Verdächtigen (1995), where the line is, "The greatest trick the devil ever pulled was convincing man that he didn't exist". In fact, that idea goes back to Charles Baudelaire (1821-1867): "La plus belle des ruses du Diable est de vous persuader qu'il n'existe pas!" (English: "The finest trick of the devil is to persuade you that he does not exist."
The bridge where the car "accident" takes place is actually the Blue Water Bridge between Point Edward, Ontario and Port Huron, Michigan. It was being "twinned" at the time, so the whole bridge was closed down for repairs, and was available for uninterrupted filming. The scenery shots of New York City were then placed in the background, but people who grew up there recognize the shores as being Point Edward and Port Huron, respectively, not New York City.
The subway station where the attack on Meg takes place is a "ghost" station on the Toronto subway that is used frequently as a stand in for New York City subways. The city's film office wanted to leave it set up as a New York City station, but the Toronto Fire Department nixed that idea. The station is below the Bay station on the Bloor line, on the track connecting the Bloor and Yonge lines. At one time, trains went from one line to the other, thus the station, but the practice was discontinued because of switching problems. (There is also a "ghost" station beneath the Queen Street station. It was roughed in 1954 for a planned Queen Street subway which never was built.)
In the original script, a character is deliberately pushed off a subway platform. This had to be changed to an accidental fall before the Toronto Transit Commission would allow filming on its property.
"Ego sum papa" roughly translates as "I am the Pope".