Sour Kangaroo

"If you can't see, hear, or feel something, it doesn't exist. And believing in tiny imaginary people is just not something we do, or tolerate here in the Jungle of Nool. You will not breathe a word of this lie to anyone else--especially the children! I don't want you poisoning their minds with this nonsense. Our community has standards, Horton. If you wanna remain a part of it, I'd recommend you follow them. Have a nice day."

- Kangaroo threatening Horton to be quiet about his belief about the speck. Sour Kangaroo, also known as Jane Kangaroo, is the (former) main antagonist of the 1954 children's book Horton Hears A Who!, by Dr Seuss, the 1970 animated television special Horton Hears A Who!, the 1992 animated film I Can Hear You, the 2000 Broadway musical Seussical, and the 2008 animated film Dr. Seuss' Horton Hears a Who!. She also appears in the Horton Hears A Who! story in the 1996 live action / puppet TV series The Wubbulous World of Dr. Seuss.

A busybody and creator of the jungle's laws, she does not believe Horton about the Whos and Whoville on the dust speck. She hires a vulture named Vlad to steal the clover bearing the speck for her. When he fails to do so, she orders her henchmen, a group of monkeys known as the Wickersham Brothers to take the speck from Horton.

After everybody was able to hear the Whos, her son, Rudy jumped out his mother's pouch and gave the speck back to Horton, much to Sour's dismay, but in the end Horton forgives her despite everything she's done to him.

She is voiced by June Foray in the 1970 television special, Carol Burnett in the 2008 film, who also played Miss Hannigan, and Stephanie D'Abruzzo in The Wubbulous World of Dr. Seuss. Sharon Wilkins portrayed Sour Kangaroo on Broadway. She's also the main antagonist in the stage musical named Seussical with all of the Dr. Seuss characters featured.