Johnny was always able to build a camaraderie with the many animals used in the Tarzan films, and he let them know he was not afraid. Especially difficult were the chimpanzees used to play Cheetah; they are notoriously vicious and unpredictable and get worse as they age. He actually worked with eight different chimps over the years.
Back in 1931 when he met the first Cheetah, the chimp challenged Weissmuller by baring his teeth in a prelude to attack. Johnny drew his hunting knife and held it closely to the Chimp’s face, and then knocked it hard against its head. After replacing the knife in its sheath, he offered Cheetah his hand. First the chimp glared at him, then grinned and took his hand. From that moment on there was a lasting bond between them, and Cheetah would snipe at anyone who came near Johnny. Maureen O’Sullivan many times has recounted how she ended up with lots of scrapes and bites from a jealous chimp!