This is about the anime characters. For the monster itself, see Jell.
The Jells are some of the most common baddies in the anime series.
The Jells first appear in Episode 3 and under the command of their captain they break into Golem's fortress to steal the lost disc resting there and take them back to Moo as spoils of war. On their way there they stop to sleep for the night and one of them gets left behind. The Searchers find him the next morning and help him out from under a fallen boulder, but he still vows to get them.
The Searchers return to the castle to find Golem pinned down, refusing to fight because he believes violence is wrong. Genki spurs him to action though and he crushes Captain Jell and several of the others. The rest flee for their lives.
The Jells are next seen in Moo's floating castle when the Searchers try to rescue Holly from her imprisonment there. Jells are also shown multiple times in flashback, as some of the first baddies that Moo created. Captain Jell was one of his ranking officers during the Final War, and Jells also played a pivotal part in the attack on Tochika. It is believed that though they report straight to Moo, the Jells often work in the employ of Naga, especially after their captain is killed.
The Jells later tangle with Niton, a peddler who makes flimsy bargains with his customers. A new captain has been appointed after the death of the first. He decides he wants Holly's dagger, and tells the Jells where the Searchers have made thier camp so that they will be captured and he can take their things. The Jells bury the Searchers in the sand while they sleep, but after they escape using Suezo's "Teleport" they beat the Jells pretty badly again.
The Jells and their captain are the first baddies to appear in season 3. Not too long after Holly finds the dark mystery disc with Moo's soul inside, the Jells come looking for it to unlock it. However, after the destruction of Moo's castle and the consequential uprising among the people of Pangaea, the Jells' numbers have shrunk considerably. Captain Jell and his small troop chase Holly and Mocchi, trying to get the disc, but after they fail and Captain Jell dies, the Jells cut their losses and turn to Durahan for help.
Durahan gives them a new captain named Pink Jam, and together they set about trying to steal the dark disc. Pink Jam disguises himself as a Muddy Jell and enters a battle competition against Mocchi. In the middle of the match, he reveals himself and tries to assassinate Genki and Mocchi in the arena. When his attempt fails and the townspeople realize he is a baddie, they chase the Jells out of town and they all begin to worry that they will never succeed at anything. That evening, Mum Mew finds a note from them saying that they've defected from the Baddies.
For the next few months, the Jells and Pink Jam travel around, trying to find work and succeed at something. But because they are baddies, people mistrust them. They come up with the idea to paint over their baddie crests so that they won't give themselves away, but even then they continue to mess up their projects. The last straw is when they are thrown out of a restaurant for preparing the food wrong.
As they wander dejectedly through the woods, they run into the Searchers again. They are taken aback when Golem offers them food, not recognizing them as THE Jells that had attacked them several times before. The Jells accept, and they all share a great evening together. The next day, the Tombstone triplets attack and try to steal the dark disc, but this time the Jells are there to back the Searchers up in the fight. Together, they put the Tombstones in the ground, and the Jells finally realize that they ARE good at something--simply being good.