Katharine Hepburn refused to reveal who wrote the screen play to Louis B. Mayer until after he bought the project from Hepburn. Hepburn was afraid that Mayer would low-ball the two authors (Michael Kanin and Ring Lardner Jr.) because, at the time, they were both relatively unknown.
At the time he met Katharine Hepburn, Spencer Tracy was already living apart from his wife, spending most of his time in his suite at the Beverly Hills Hotel, while his wife and children lived on a ranch in the San Fernando Valley.
One major difference between the stars was that Katharine Hepburn loved to rehearse while Spencer Tracy preferred to work more spontaneously and often gave his best performance on the first take. Hepburn had to adjust to his approach to hold her own.
Knowing of Spencer Tracy's reputation as a heavy drinker, Katharine Hepburn served him strong tea between scenes. She also got him to paint, as she did, as an escape from the pressures of Hollywood life.