Jerso

Jerso (ジェルソ) (also spelled Jelso) is a military operative who was under the command of Solf J. Kimblee.

Background
He was used as a test subject in military experiments and is now a human chimera capable of transforming into a strange, toad-like creature resembling a bipedal Frogfish. He is partnered with Zampano.

Part in the story
While being part of the military, Jerso and his partner Zampano were Kimblee's bodyguards. In Bascool, Jerso and Zampano manage to track Scar and they battle. Due to their intelligence on Scar's battle strategy, they almost manage to beat him until the Elric Brothers show up and knock out the two chimeras and restrain Scar. Before Major Miles has a chance to execute Jerso and Zampano, Alphonse convinces them to come with them on the promise that they may be able to get back their original bodies. They escape in the old mine shaft with Scar, Dr. Marcoh, May Chang, and Yoki.

While in a small Ishvalan refugee camp, the group confronts Envy after Zampano tips him off to their location. Zampano actually tricks Envy into coming there to fight them, and plays a part in the battle against the homunculus. May's long-range alchemy, his and Zampano's attacks, and Marcoh's Philosopher's Stone are what ultimately defeats Envy.

After May is supposed to return to Xing with a weakened Envy, the rest of the group travels toward Reole where Zampano, Jerso, and Yoki would help with the rebuilding. After the time-skip, they head towards Central and meet up with Edward, Darius, Heinkel, Lan Fan, Fu, and Hohenheim. They aid in Mustang's invasion of Central, infiltrating the bowels of the city and capturing the Gold-Toothed Doctor with his spit. He is then wounded by Pride and drops the Doctor to the ground as he falls. He is incapacitated for the rest of the battle due to his injuries. At the end of the series, he is last seen with Zampano in a café, discussing different methods to get their bodies back, and are about to set off to Xing with Alphonse as his bodyguards.

Abilities
Jerso is a human-based chimera and can transform into a large amphibious or Antennariidae-like monster, though without any Spinule. While in this form, he can spit an extremely sticky saliva that can immobilize his targets and can also move quite fast for his bulbous size. He never demonstrated any of his hybrid's powers while in human form but he likely has some excess power while in human form since other Chimeras retain such abilities similarly.

Trivia

 * The names of Jerso and his companion Zampano may have been derived from that of the two main characters, Gelsomina and Zampano, in the 1954 Italian film La Strada, directed by Federico Fellini.
 * Jerso's Japanese voice actor Tomoyuki Shimura also voices Breda in the 2003 series.
 * Though the author appears to have intended to model Jerso's form after a frog or toad, with the anime's last scene with Jerso making it clear to be one or the other, his upper body resembles that of a Frog fish, a type of angler fish resembling an amphibian.
 * Despite his name being "Jerso", in the end credits of the English dub, he is referred to as "Gerso".