Sour Kangaroo

Sour Kangaroo is the main villain of Horton Hears a Who! Her real name is Jane Kangaroo. She doesn't believe Horton about the Whos and wishes to brutally slay him in a highly gruesome fashion. Kangaroo 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. Her henchmen are a group of monkeys known as the Wickersham Brothers. She orders them to take the speck from Horton. When they fail to do so she talks to a vulture named Vlad to steal the speck for her.

After everybody was able to hear the Whos, Kangaroo's son, Rudy jumped out his mother's pouch and gave the speck back to Horton, much to Kangaroo's dismay, but in the end Horton forgives her and becomes good.