The Jester is something that resonates with my own personality, so for me, they are extremely natural and fun to play!
I created a Jester NPC for a mini-campaign once, based on articles found in Dragon Magazine 60 & 120. He was a Sprite and functioned as a adventure-causing catalyst in the sessions. The character mostly dealt in puns, illusions, pranks and general harassing of the Big Folk. I still take that character out of mothball once in a while and have him appear in the wilderness settings he was originally created for.
Later on, I had a Rogue PC that had some shades of Jester in him, especially when he was on a vengeance kick. He was in an Immortals game and like the chaotic god Balor in Moorcock’s Elric cycle, he was not always something to laugh at! Indeed, he would appear as a similar sort of clown, juggling fire which became a devastating weapon. People were not usually laughing after his performance!
The mythology behind clown, Jesters and Trickster gods is that way. They can be full of wisdom, mischief and folly as sometimes the joke is on them.
Kokopelli is a well-known iteration of a Trickster.
The figure represents a mischievous trickster or the Minstrel, spirit of music. Kokopelli is distinguished by his dancing pose, a hunchback and flute. His whimsical nature, charitable deeds, and vital spirit give him a prominent position in Native American mysticism.
Kokopelli has been a sacred figure to Native Americans of the Southwestern United States for thousands of years. Found painted and carved on rock walls and boulders throughout this region, Kokopelli is one of the most intriguing and widespread images to have survived from ancient Anasazi Indian mythology, and is a prominent figure in Hopi and Zuni legends. Kokopelli is also revered by current-day descendants including the Hopi, Taos and Acoma pueblo peoples.
Kokopelli is considered a symbol of fertility who brought well-being to the people, assuring success in hunting, planting and growing crops, and human conception. His “hump” was often considered a bag of gifts, a sack carrying the seeds of plants and flowers he would scatter every spring. Warming the earth by playing his flute and singing songs, Kokopelli would melt the winter snow and create rain, ensuring a good harvest. Kokopelli often displayed a long phallus, symbolizing the fertile seeds of human reproduction.
Many peoples world-wide have their own myths about these Jester-types, so you may want to explore them for the cultures in your own campaign.
Sometimes a Jester player character is hard to integrate well into a campaign, but it can be done, if the player is skillful and the conditions of the campaign are right. I tend to find them more useful as an NPC and they can really stir things up and cause the PCs to take notice of things that they might otherwise not have any interest in dealing with. My NPC would snatch valuable magical items from PCs and lead them on a wild goose chase into some odd adventures, only to give the item back later time, thanking the PCs for such a wonderful play time. A Jester could lead the PCs through encounters that are serious and life-threatening to them, but that affect the NPC not at all, because of their buffoonery.
A Jester NPC is best used sparingly in most cases, but if played right, they can really liven things up! I would try to avoid totally irking the characters and use some restraint, though, or like the Trickster gods, the joke may be on the DM as they are the only one left at the gaming table when the players give up in frustration!
Whatever your take on Jester-types, if used well, a Trickster makes a fun and odd interjection into an RPG world.