Sour Kangaroo, aka Jane Kangaroo, is the main antagonist of Horton Hears a Who she is a busybody and creator of the jungle's laws who is skeptical about the existence of the Whos and Whoville on a dust speck (due to being under the pretense that anything which cannot be seen, heard or felt is nonexistent). She also is mother of Rudy Kangaroo, who thinks her to be very embarrassing. She is a major antagonist in the first season of The Wubbulous World of Dr. Seuss and a supporting character in the second season.
Jane serves as the main antagonist of the film. As Horton's claims begin to drive her towards darkness, she believes that once other people start listening to Horton, they'll start to come to her with questions she won't be able to answer. In order to avoid this, she begins making deals with the Wickershams and the vulture hitman Vlad Vladikoff. As the film progresses, her aims start to shift towards crushing Horton's spirit and building up her own reputation. The Kangaroo is too dismissive of the products of imagination and creativity, even to the point where she keeps her son Rudy jammed inside her pouch. She believes that outside the "comfort" her ideas provide him, non-conformity and anarchy are minutes away from turning their ordered life into chaos. Yet, in the end, Horton's convincing changes her mindset.
In Seussical, she thinks Horton is crazy for talking to a speck, spreading the news around and causing big trouble for Horton. In the TV Special, There Is Not One Kangaroo, But 5 Kangaroos and they are children, 3 boys and 2 girls.
In the book she's a yellow kangaroo. In the Seussical TV special, the kangaroo children are pink, orange, yellow, blue and purple with round heads. In the film she is purple with turf of fur around her neck and long hair on her that stands up straight.