One of the first films (preceded by Stage Door (1937)) to have characters talk over the lines of other characters, for a more realistic sound. Prior to this, movie characters completed their lines before the next lines were started.
It is estimated that the normal rate of verbal dialogue in most films is around 90 words a minute. In His Girl Friday (1940), the delivery has been clocked at 240 words a minute.
Rosalind Russell thought, while shooting, that she didn't have as many good lines as Cary Grant had, so she hired an advertisement writer through her brother-in-law and had him write more clever lines for the dialog. Since Howard Hawks allowed for spontaneity and ad-libbing, he, and many of the cast and crew didn't notice it, but Grant knew she was up to something, leading him to greet her every morning: "What have you got today?"
Right after Williams is found in the desk, the Mayor tells Walter that he's "Whistling in the dark. Well that isn't going to help you this time. You're through." Walter says "Listen the last man that said that to me was Archie Leach just a week before he cut his throat." Archie Leach was Cary Grant's birth name.
During the 1930s, Howard Hawks was hosting a dinner party when the topic of dialogue was brought up. He pulled out a copy of "The Front Page" to demonstrate the snappy exchanges between characters, taking the role of Burns. A female guest took the role of Hildy. While reading, Hawks realized the dialogue sounded much better with a woman reading, and quickly secured the rights for the film from Howard Hughes. Ben Hecht (the author of "The Front Page") approved the gender change and the screenplay was put into production.