Incredibly, Howard Hawks’ classic screwball comedy Bringing Up Baby flopped when it was originally released in 1938. The movie came in over budget, was delivered to its studio late, and despite positive reviews only just managed to break even at the box office—leading to its star, Katharine Hepburn, being memorably labeled “box office poison” in the late 1930s.

The role of a scatterbrained heiress Susan Vance—the owner of the titular pet leopard Baby—had been specifically written for Hepburn, but she reportedly struggled with the fast-paced comic timing of the script, and resorted to asking a fellow cast member, vaudeville comic veteran Walter Catlett, to help her with her performance. One thing Hepburn did not struggle with, however, was acting opposite a live leopard.

Known as “Nissa,” the leopard was almost as much of a movie veteran as its co-star: By 1938, she had already made several appearances in a string of Hollywood B-movies. Nissa was accompanied on set by a handler, who was armed every day with a whip in case she failed to act as commanded. One such day came when Hepburn, dressed in a long flowing skirt with silver trim, turned her back too quickly in front of Nissa, causing the hem of the skirt to twirl around in the set lights. Like any cat, Nissa responded inquisitively—by lunging at Hepburn’s back. Thankfully, a whip-crack from her handler quickly brought the animal back under control…

Despite that run in, Hepburn remained largely unfazed by Nissa; she posed for several publicity photographs with her and would often pet her between takes. Her co-star, Cary Grant, however, was less keen.

Grant was so nervous around Nissa that a body double was used for any scene in which his character had to interact with or touch her. Knowing how uncomfortable Grant was around Nissa, however, Hepburn decided to get the better of him and had one of the workers on set place a life-size toy leopard behind the grille of an air conditioning vent in Grant’s dressing room. “He was out of there like lightning,” Hepburn later recalled.