As soon as the words are out of Horton's mouth, a bunch of jungle animals (those nosy kangaroos and apes!) come out of the woodwork to say that they're tired of Horton talking to his "imaginary" friends.
The Wickersham Brothers and their entire family have decided that they're going to cage up Horton and boil the speck of dust in a kettle of Beezle-Nut oil.
Horton is horrified. And to be honest, so are we.
Horton calls out to the Whos and tells them that they must make as much noise as they can so that the other animals will believe that they exist.
The Whos go for it: they start screaming out to literally save their own lives. But sadly, none of the other animals (except for Horton) hear anything at all. Must be those big ears.
Poor Horton. The animals lasso him up even though he fights back pretty hard. He yells to the Mayor of Who-ville to never give up.