The Jester is the main antagonist of Dorothy of Oz.
Dorothy of Oz
In Dorothy of Oz, the Jester had gotten his hands on a wand of the Wicked Witch of the West and was possessed by her ghost. Under the Wicked Witch of the West's possession, the Jester used the wand to turn Princess Gayelette, Prince Quelala, and their dinner guests into China Dolls. He even managed to do the same thing to Scarecrow, Tin Man, and Cowardly Lion as well as abduct the China Princess from the Dainty China Country. When Dorothy Gale and Toto arrived in Princess Gayelette's kingdom, they run into the Jester who points them to Princess Gayelette's castle. When Dorothy learns about the Jester's actions, she returns to the main hall and found that the Jester had turned Toto into a China Doll as the Jester shows Dorothy his China Doll collection. Dorothy came up with an idea to bring Glinda to the Jester under the condition that Toto, Scarecrow, Tin Man, and Cowardly Lion assists her. The Jester agrees to Dorothy's deal, but Toto will remain with him.
When the Scarecrow, Tin Man, and Cowardly Lion slipped into their China Doll disguises upon arrival outside of Princess Gayelette's castle, Dorothy then meets up with the Jester who shows Dorothy his collection which is now on the outside. Dorothy takes the Jester to the red wagon where Dorothy has him open the crates where she claims that Glinda is in one of them claiming that Glinda turned herself, Scarecrow, Tin Man, and Cowardly Lion into china dolls. Dorothy then hears the voice of the Wicked Witch of the West's ghost who suspects a trick and orders the Jester to turn Dorothy into a china doll quickly. As the Wicked Witch of the West's ghost continues to warn the Jester of Dorothy's trick, the Cowardly Lion's tail came out of his disguise as the Jester prepares to attack. Dorothy reminds the Jester that jesters are supposed to make people happy causing the Jester to freeze in his tracks as the Wicked Witch of the West's ghost urges the Jester to turn Dorothy into a china doll. The Jester gives up the wand as the Wicked Witch of the West's ghost fades away. Thus, the spell is broken and everyone is returned to normal. Scarecrow, Tin Man, Cowardly Lion, and Toto rejoice now that the spell is broken. When Dorothy asks Princess Gayelette and Prince Quelala if the Jester can stay and jest for them again as a way to prove that he is sorry, Princess Gayelette accepts Dorothy's deals and has the Jester entertain them again.
Legends of Oz: Dorothy's Return
The Jester appears in Legends of Oz: Dorothy's Return voiced by Martin Short. In this film, the Jester has a Kansas counterpart in the form of a con artist posing as a Government Appraiser. He is supposed to be the brother of the Wicked Witch of the West as she is seen in the 1939 MGM film. Despite it is not clearly told in the film, it seems that the Witch of the West didn't appreciate her brother at all, and cursed him (for an unknown reason): he is condemned to always wear a Jester outfit which makes that he never seems serious and is a bit ridiculous in everything he does.
After the events of the first film, the Jester robs her dead sister's Magic Broomstick from the Scarecrow (who was keeping it in the Emerald City), and uses it to control the Flying Monkeys in order to rule Oz. Happily, the Scarecrow (who in that version really became a genius until he saw the Wizard of Oz) found a technological way to bring back Dorothy from Kansas, so she can defeats the Jester (which is eventually what happens).