Kaa is normally the secondary antagonist of The Jungle Book and it's sequel. He is the younger version of the secondary antagonist of The Jungle Book. He is also a supporting antagonist turned-anti-hero in it's 1994 live action film, one of the main protagonists of it's prequel television series Jungle Cubs, a recurring character in several other Jungle Book related sources, such House of Mouse, and an antagonist in Mickey's House of Villains.
He is voiced by the late Sterling Holloway in the original film, Hal Smith in 1977 and currently Jim Cummings.
In the 2016 film, Kaa is portrayed as female and is voiced by Scarlett Johansson.
In Jungle Cubs, Kaa does not appear to be a predator or a villain possibly due to him being a young cub, but in the films, he's a villain and a predator. He is portrayed as a young cub, and used to be friends with Baloo, Hathi, Louie, Bagheera and Shere Khan, and was considered as one of the main characters and a protagonist, much like the non-disney Kaa.
He does not appear in Tail Spin, like Shere Khan does.
The only TV shows he appears in are Jungle Cubs and House of Mouse.