From the Super Mario Wiki
Jesters are clowns that work for Booster in his amusement tower. They wear white masks, red hats, and large white gloves. In combat, a Jester's primary attack is hitting an intruder with its massive hand. They can also use cards to deliver damage. Finally, a Jester can use Flame Stone, which causes a fireball to fall from the sky and crash into an opponent, causing massive damage.
Among the unused sprites of Super Mario RPG: Legend of the Seven Stars, there is an enemy named Harlequin, which is a Jester lookalike. The only noticeable differences is Harlequin's green color and the lack of Magic Attacks. Its psychopath thought is "Kekekekekekekekekeka!"
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