Cary Grant introduced Rosalind Russell on set to producer Frederick Brisson. They married a year later. (And no, they never divorced.) (Source)

Russell felt she didn't have as many good lines as Cary Grant, so she hired her own scriptwriter to add some better ones. Hawks allowed for ad-libbing, so Russell would sneak her pre-written lines in during shooting. (Maybe Russell was ever sneakier than Walter, huh?) (Source)

The first choice to play Hildy was Jean Arthur, who turned it down. Carole Lombard, Ginger Rogers, Claudette Colbert, and Irene Dunne also turned it down. Everyone turned it down, just about, before it was offered to Rosalind Russell. She was a little bitter about that—who can blame her? (Source)