In the original novel written by Burroughs, Kerchak is the "king" of a tribal band of Mangani, a fictional species of Great Ape intermediate between real life chimpanzees and gorillas. In the beginning of the original novel, Kerchack leads his band against Tarzan's marooned parents and kills them; the infant Tarzan is saved by a female Mangani named Kala, who rears the baby and protects him against Kerchak. When Tarzan reaches adulthood, he fights and kills Kerchak and succeeds him as king of the apes.
Kerchak's character in the Disney adaptation (1999) was changed substantially from his original role in the series. In the Disney version, Kerchak's character is downplayed as a protagonist instead of an antagonist. Kerchak in the film had no role in the slaying of Tarzan's parents. In the film, he is portrayed simply as the over-protective leader of the ape group, as well as the mate to Tarzan's adoptive mother, Kala. Kerchak shuns Tarzan for his childhood (tolerating him only out of respect for Kala), but accepts him in adulthood when Tarzan proves himself as a legitimate leader and protecter of the group by killing the threatening leopard named Sabor, and saving the group from the hunter named Clayton. Kerchak is shot by Clayton when trying to protect Tarzan, and passes his leadership position onto Tarzan willingly (and also accepting him as his adopted son at last) before he dies from his injury.
Following real life apes, Disney also made Kerchak a silverback gorilla; which is the name given to mature male gorillas because of the silver hair covering their backs. Kerchak was voiced by actor Lance Henriksen.
The film's Kerchak is essentially a combination of the novel's Kerchak and another of the novel's ape characters, Tublat. In Burroughs's original story Tublat was Kala's mate, a fairly passive figure resentful of his foster-son Tarzan. The Kerchak of the film is closer in personality to Tublat than to the original Kerchak. However, in the spin-off series "The Legend of Tarzan", Tublat appeared with a personality much like the original Kerchak, being violent and seeking revenge on Kerchak through Tarzan (being his successor as leader of the gorillas), having been cast out many years ago after he challenged Kerchak for leadership and lost.
Kerchak also appears briefly in the video game Kingdom Hearts. With no speaking lines, Kerchak first appears when Tarzan pleads with him and Kala to help him aid Sora, Donald and Goofy (in ape language, which the trio do not understand). Kerchak initially does not trust the trio, and matters are made worse when Clayton almost kills Terk, for the timely intervention of Donald (on whom Terk later develops a crush). However, Kerchak later comes to accept the trio after they defeat Clayton and his Heartless companion, the Stealth Sneak, and allows them access to the world's Keyhole, which Sora seals, protecting the world from the Heartless permanently.
Interestingly in the original film Kerchak died after being shot by Clayton, whilst in Kingdom Hearts he lives on. It's unknown if he had passed his leadership position onto Tarzan like he did in the film.