Hawks instructed RKO to purchase the short story’s rights, and author Hagar Wilde was brought in to work on the script. Screenwriter Dudley Nichols later joined her, and the pair used their own romance as kindling for the plot’s love story. It’s been suggested that the dynamic between Katharine Hepburn and director John Ford, who worked together on Mary of Scotland, also served as an inspiration as Nichols also wrote that screenplay.

Hawks wanted Carole Lombard for the female lead, having worked with her in Twentieth Century. The studio, however, was keen on using Katharine Hepburn who was under contract, with three films left to make. Despite winning an Academy Award in 1934 for Morning Glory, Kate was having a hard time finding her next success. Unfortunately, despite her hilarious performance, Bringing Up Baby  wouldn’t help turn the tide and actually got her labeled (as absurd as it seems now) “box office poison.”

For the male lead, Hawks wanted Harold Lloyd and then Ronald Colman. Instead, the studio gave the go-ahead for hiring Robert Montgomery, Fredric March and Ray Milland, but all of them turned down the part. Eventually, Cary Grant was suggested since he also had a contract with RKO and was hot off the success of The Awful Truth. Ironically, even though Harold Lloyd wasn’t cast, Grant’s performance and look (including the glasses) were inspired by the comedian. Hawks and Cary would work on four more films together.

A key detail revolves around the lead characters singing 1928’s “I Can’t Give You Anything But Love” to calm down the leopard (which was originally a panther). RKO purchased the rights to the song for $1,000 dollars. They also had to purchase the rights from a comic strip “Professor Dinglehoffer and His Dog” by Harold Knerr, when they used the storyline of the dog burying a dinosaur bone.

Hepburn said, “I was the only one who would work with the leopard because Cary was so scared of it. I was too dumb to be afraid.” During the production, Hepburn pranked Grant and planted a fake leopard in his dressing room. Grant, of course, had a right to be cautious around the big cat, and Kate almost had an accident. When filming, the sound of one of her dresses caused the leopard to spring at her back. After that, the leopard didn’t mix with the actors.

Kate wasn’t used to playing comedy, and she struggled in delivering her lines. So Hawks hired vaudevillian Walter Catlett to coach her. Hawks said, “And from that time on, she knew how to play comedy better, which is just to read the lines.” Hepburn asked Hawks to keep Catlett nearby, and so he also got a chance to be in the film, playing a policeman.

The part of George was played by a Wire Fox Terrier named Skippy, who was quite the Hollywood professional, having starred as Asta in The Thin Man series. Cary Grant had actually previously worked with his canine co-star in The Awful Truth. Skippy was a graduate of a dog training school whose alumni included Lassie dogs and Toto from The Wizard of Oz. Rightfully so, he got his own dressing room, lots of fan mail, and $250 dollars a week. However, his true motivation for working was a rubber mouse toy.

RKO wanted a quick picture that would be completed in 51 days. What they got was a film that went approximately $300 thousand over budget and took 91 days. The delay was due to the improvisational method used by Hawks, which produced some of the funniest lines and gags, but also required more time. At one point, the assistant director remarked to the studio that “virtually no line in the film is identical to the one called for in any script.”

Cary Grant was at the Roxy Theater when the head of the Metropolitan Museum stood to let his wife pass and noticed his pants were unzipped. As he remedied the situation, her frock caught in the zipper, and they had to lock step out to get help. Grant told the funny story to Hawks who added it into the film, nixing the fly bit so as not to upset the censors. Grant’s circus training was also helpful as he taught Hepburn how to grab his wrist, not his hand, when jumping off the falling dinosaur. He said, “Kate was marvelously trusting if she thought you knew what you were doing.”

His character served as the inspiration for Téa Leoni’s absent-minded Egyptologist in Ghost Town (more on that here) and for Christopher Reeve’s Clark Kent in Superman. Peter Bogdanovich’s What’s Up Doc?  also borrowed heavily from Bringing Up Baby, where Ryan O’Neal and Barbra Streisand played similar types to Grant and Hepburn. Bogdanovich said, “Cary is a great comedian and a great dramatic actor. He can do anything.”