JoJo is a small Who (the smallest of all) who provides the voice needed to make the other animals hear Whoville and realize Horton was telling the truth.
Jojo is only given a distinct personality in the Illumination feature film adaption of Horton Hears a Who, and Seussical the Musical.
Blue Sky Film
Jojo is the son of Ned McDodd and he is oldest child, as well as the only boy, among the Mayor's 97 children, and will more than likely be the future mayor of Whoville, because in Whoville tradition "the oldest is next in the mayoral line". JoJo is also the smallest Who of all.
JoJo is so worried that he'll say something to disappoint his father that he finds it best not to speak- ever. But he's anything but silent. He hears music in the tapping of an old keyboard, feels the beat in the rhythmic bounce of a basketball and finds harmony in wind whistling over a comb.
It is later revealed that JoJo takes nightly excursions to the Abandoned Star-Study Tower, and the one time we see him about to leave, his arms are filled with various odds and ends (including an umbrella that looks remarkably like that of the Cat in the Hat's), are to work on what is rather literally a giant instrument (called "the Symphonophone" on the soundtrack): he had filled the observatory with these castaway items and set up an elaborate system to produce music. JoJo uses his Symphonophone to add to the ruckus needed to alert the citizens of Nool to their existence, in addition to his signature cry: "YOPP!"
Seussical the Musical
In Seussical the Musical, Jojo is the protagonist, and acts as an energetic young boy (or sometimes girl, depending on the production) with big ideas. He is curious, and often gets into trouble. He befriends Horton, who has similar problems to him.
In the special, JoJo is blond, has blue eyes, and wears an all-blue outfit with a red bowtie around his neck.
Seussical the Musical
Jojo also appears in Seussical the Musical as the protagonist. Jojo keeps getting in trouble for having different thoughts and big ideas. The Cat in the Hat also keeps popping up and getting him into even more trouble. He then meets Horton, who also has problems because of his big ideas (And of course because he thinks there are people on a speck of dust).
He begins the show as an unnamed kid, who upon letting his/her imagination run wild, summons the Cat in the Hat to the stage, beginning the show. The Cat tells him/her about Thinks, and all sorts of Thinks you can think, in the opening number. He imagines the Jungle of Nool, and Horton the Elephant, kicking off the story of the show, and proceeds to watch from afar with the Cat, speaking up from time to time.
Eventually, the Cat pushes Jojo into the story, taking the role his name would imply, as the Mayor's son. Through the Mayor and his wife, it is learned that Jojo is a well-rounded kid, but has been acting very strange lately. He has been thinking strange thinks, causing problems at school. Learning this, the Mayor and Mrs. Mayor chastise Jojo, urging him to think a bit less.
For a moment, Jojo attempts this to avoid getting into trouble, but with a little urging by the Cat, he ends up imagining his bathtub as McElligot's Pool. He sings about the possibilities that come with Thinks, but he is ultimately interrupted by his parents, who hurry in after he has flooded the bathroom with the water from the tub. They make it clear to him that he's in quite a lot of trouble.
With little idea of what to do now, the Mayor and his wife decide to send Jojo off to the military, helmed by General Genghis Khan Schmitz. Jojo agrees, reluctantly, to head off with them soon. That night, he meets Horton the Elephant, who communicates to him when searching for someone on the speck Planet Who lives on to talk to. The two form a bond over their shared love of Thinks and their big imaginations. For the rest of Act I, Jojo is only seen along with the Cat.
He is seen momentarily at the beginning of Act II, pleading to the Cat to know what happens to all of the characters. The Cat playfully informs him that a whole second act is on its way, and he only need be patient.
Jojo is next seen near the end of Act II, writing a letter to his parents, and wishing they were all in Solla Sollew, taking part in the number under the same name with his parents and Horton.
He marches with General Schmitz and his cadets to the war zone in order to defeat the Butter-Side Uppers, but ends up questioning the General's logic, telling him it's pointless to fight, and that it doesn't matter which side one eats their bread. He also informs the General (and the audience) that it's Christmas on Who, and he'd much rather be celebrating. He hands the General his sword, and attempts to go home. The General tries to stop him, but Jojo gets lost in the forest.
When the General returns to Whoville claiming Jojo was lost in the battle, it is assumed that he has perished. However, the Cat proposes that he survived, and then brings the audience to him. Jojo is lost in the forest, and he's being surrounded by Hunches, not sure if he'll ever make it home. Jojo lashes out at the Cat, blaming him for all the trouble the he's gotten the boy into. He tells the Cat to leave, but first the Cat proves to him that the Hunches are simply all in his head. Using his Thinks, and a bit of advice from the Cat, Jojo does manage to make his way home to his parents, who are relieved to see him, and seem to finally realize the power of Jojo's thinks when they are able to bring him home.
With Jojo's conflicts solved, the events of Horton Hears a Who! carry out very similarly to how they do in the book. The clover carrying the dust speck that is the Whos' home is about to be boiled by the citizens of the Jungle of Nool. Horton urges the Whos to yell to the skies, "We are here!" But it doesn't seem to be enough. At the last minute, the Mayor, Mrs. Mayor, and Horton all call out to Jojo to think of something.
Jojo thinks of a new word that no one has ever heard of before. He cries, "YOPP!" Stunned, the animals of the Jungle of Nool finally hear the Whos, and decide to help Horton guard them from harm. Safe at last, the Whos honor Jojo as Thinker Non-stop.
- He only has four to five lines lines in the film:
- (silently mocking his dad) "Good talk."
- "Dad, you're one of the greats!"
- "What are we gonna do without you, Horton?"
- (singing) "I can't fight this feeling any-MORE!!!!"
- Technically in the Blue Sky Film, the statment that he is the smallest Who is incorrect, as Hedy, his youngest sister, is smaller than he is. However this may be due to her young age, while JoJo is still smaller than the rest of his sisters.
- JoJo's singing voice at the end of the film is provided not by Jesse McCartney, but by session singer Fletcher Sheridan, who was in another Dr. Seuss film, The Lorax, as Cy, the O'Hare delivery guy.