The Whos try to get their voice heard by ensuring that all Whos play their part.
In the end it is a “very small shirker named JoJo” whose final addition to the volume creates enough lift for the jungle to hear the sound, thus reinforcing the moral of “a person’s a person, no matter how small”. Now convinced of the Whos’ existence, Horton’s fellow jungle animals vow to help him protect the tiny community.
In the end, the Whos are collectively making as much noise and racket as they possibly can. Every inhabitant of this tiny spec of dust is working together in cooperation to achieve a common goal of survival of their common world.
A lesson we can follow if the survival of our own tiny spec of dust is ever at stake.