* DawsonCasting: Both leads were older than their characters. Amusingly, Hitchcock denied JimmyStewart the part of Thornhill because he thought he was too old for it - so instead he got Cary Grant, who was even older than Stewart.
* HeyItsThatGuy: The Professor is [[TheManFromUNCLE Alexander Waverly]]. Leonard is [[MissionImpossible Rollin Hand]]. Roger's lawyer is [[Series/GetSmart The Chief of CONTROL]].
* ImageSource: This film provides the page image for:
* ThrowItIn: An unintentional one. When Eve [[spoiler: shoots Roger in the restaurant with the blanks]], a child actor covers his ears before the gunshot happens. The take was still used, since aside from this, it was the best take.
* WhatCouldHaveBeen: While the film was still in the early scripting stage, a scene taking place at an assembly line in Detroit was envisioned, where the camera would follow two men as they talked while a car was built behind them piece by piece...and at the end, one of the characters would open a door of the now-finished car and a corpse would fall out!
* WordOfGay: Martin Landau stated in interviews that he portrayed Vandamm's henchman Leonard as a closeted homosexual who was secretly jealous of Eve Kendall's relationship with his employer. In the scene where he revealed to Vandamm that Eve was secretly working for the Feds, he commented, "Call it my woman's intuition if you will..."
* WorkingTitle: ''The Man in Lincoln's Nose''.