Terk the Gorilla loves the spotlight, and she's perfect "big sister" material because she's Tarzan's closest friend—protective, concerned, and absolutely convinced that Tarzan can't survive without her. Terk loves telling Tarzan what to do—that is, until Tarzan's physical strength proves he can hold her in a headlock instead. Even though Terk is a bit bossy at times, Tarzan knows it's because Terk cares, though she will never say so willingly.
In the movie, Terk is one of the young gorillas in Tarzan's Ape Family and she is the first to spot Kala coming back with Tarzan. When Terk first sees Tarzan she calls him creepy looking, to which her mother scolds at her for saying and Terk asks Kala what Tarzan is and Kala tells her that he's a baby and puts Tarzan in Terk's arms to which Tarzan starts playing with Terk and when Terk asks where Tarzan's mother is, Kala simply says she will be his mother now. Terk hands Tarzan back to Kala and tells Kerchak, the Leader, that Kala's going to be the baby's new mother. After Kerchak allows Kala to keep Tarzan, Terk asks Kala what she's going to call him, and Kala says that she's going to call him Tarzan. After that, Terk's mother picks her up and tells her that it's way past her nest time. Just before she went to sleep, Terk slid off her mother's belly, picked a leaf for a blanket and climbed back on her belly. When Tarzan grows into a little boy, he accidentally runs into Kerchak, but Terk manages to help Tarzan by acting that she was looking for him, and takes him away from Kerchak.
Terk then orders Tarzan to stay away from Kerchak and then runs off to join two ape boys named Flynt and Mungo to which Tarzan asks Terk if he can come to which Terk says that Tarzan could come if he could keep up but he can't keep up. Terk then runs off to join Flynt and Mungo but soon Tarzan appears telling Flynt and Mungo that Terk said that he could come if he could keep up to which Flynt and Mungo complain that Tarzan is there and Terk takes aside and tells him that in order to convince Flynt and Mungo that he's cool enough to hang out with them he needs to go and get an elephant hair off an elephant's tail which is pretty dangerous and she tells Tarzan to go home but when Terk turns her head around Tarzan jumps into the water and swims towards the elephants to which Flynt and Mungo tell Terk that if Tarzan lives she should bring him around more often and leave to watch Tarzan get an elephant hair.
While trying to acquire the elephant hair, Tarzan is seen by the elephants and mistakenly assumed to be a piranha, causing the elephants to stampede in panic. Flying and Mungo are able to outrun the elephant herd, but Terk is caught on a vine and is swung up onto a nearby branch, allowing the elephants to pass safely beneath her. She then returns for the unconscious Tarzan, pleading with him not to die as she drags him from the water. After regaining consciousness, Tarzan accepts responsibility for causing the stampede and is scolded by Kerchak, who openly proclaims that Tarzan will never be one of the family. Tarzan then resolves to become "the best ape ever," an endeavor which Terk assists him in.
For a while Terk is clearly superior, but over time Tarzan becomes stronger and more athletic (the only character observed to be able to swing from vines), he also displays a higher degree of intelligence and ingenuity than the other Gorillas. Years later when Terk is a mid-sized adult gorilla, Tarzan, Terk, andTantor are talking when Sabor the Leopard appears and attacks the gorilla family but Tarzan manages to fight the leopard to which Terk and the other gorillas cheer him on. After defeating Sabor, Terk and the other gorillas cheer for Tarzan and Terk tells him not to make that into a habit because there are other ways to get attention. Then they hear gunshots in the distance and Terk along with Tantor follow the rest of the gorillas as they move deeper into the jungle while Tarzan sneaks off to find out what that sound is. Later on Terk, Tantor and some of the other ape boys are out looking for Tarzan when they come across the humans' camp to which Tantor freaks out at the humans' stuff, but Terk replies, "These things aren't alive." Deeply curious, Terk, Tantor, and the ape boys use the humans' stuff to make up their own music (Trashin' the Camp song).