Leo Fitz and Jemma Simmons
Jemma Simmons and Leo Fitz
Gender Male (Leo Fitz)
Female (Jemma Simmons)
Species Human
*Human mutate (formerly)
Affiliations S.H.I.E.L.D.
Occupation S.H.I.E.L.D. agent
*S.H.I.E.L.D. scientist
Status Alive
First appearance "Lizards"
Voiced by Iain De Caestecker (Leo Fitz)
Elizabeth Henstridge (Jemma Simmons)
"Oh, and did I forget to mention Agents Fitz and Simmons—two of the greatest S.H.I.E.L.D. techs of all time—are helping upgrade the Triskelion?"
Spider-Man, on Fitz and Simmons.[src]

Leopold James "Leo" Fitz and Jemma Anne Simmons are two S.H.I.E.L.D. agents and scientists. Hailed as two of the best technicians in the agency, they are called in to help rebuild and upgrade the Triskelion after Hydra destroyed it.


"Welcome, Academy students. Today, we've got some upgrades that will certainly blow you away."
"Not literally, we hope."
"Aha! Yes. You will be
figuratively blown away. Quite figuratively."
—Simmons and Fitz to the S.H.I.E.L.D. Academy students.[src]

After Doctor Octopus and Hydra's assault on the Triskelion, Fitz and Simmons are brought in to help repair and upgrade the base. As part of the reconstruction, they upgraded the training robots for the S.H.I.E.L.D. Academy students. During one of the training sessions, a robot malfunctions and attacks Spider-Man, much to their surprise. Before fleeing to safety, Fitz and Simmons warn the students that the robot's fail-safes are off and attacking with lethal force. After Rhino destroyed the robot, Fitz and Simmons apologize for the mishap and return to their lab to examine its remains. Believing that the robot's malfunction was caused due to sabotage by Doctor Octopus's spy within S.H.I.E.L.D., Spider-Man and Iron Spider visit Fitz and Simmons in their lab as part of their investigation. Upon arriving, Spider-Man notices a particular device on one of the tables, prompting the scientists to explain that the device is an aerosol dispersal unit prototype that they developed, which is designed to administer tranquilizer gas and capable of knocking out an entire building with a single vial.

Iron Spider suggests that the robot's malfunction was due to sabotage, but Fitz and Simmons tell the two heroes that sabotage was an unlikely possibility, as the training robots were moved directly to the Triskelion from the factory and then calibrated onsite. Fitz also points out that it would be impossible to know if the robot that attacked Spider-Man was reprogrammed since its central processor was destroyed by Rhino's attack. However, he and Simmons remain confident that the robot merely malfunctioned since glitches were expected to occur when upgrading the Triskelion. When Spider-Man asks who was in charge of calibrating the robots, Simmons informs him that it was Dr. Curt Connors. As the pair verify the Spider-Men that glitches rarely happens, another machine goes haywire and forces the two heroes to evacuate the lab.

When Dr. Connors is forcibly turned back into the Lizard and begins transforming S.H.I.E.L.D. personnel into lizards with his contagious bite, Fitz and Simmons hide in the floor vents. With only one vial of the Lizard cure remaining, Spider-Man and Iron Spider make their way back to Fitz and Simmons's lab, and discover them in the vents. The four S.H.I.E.L.D. agents then crawl through the vents to access the lab and use a chemical synthesizer to synthesize the cure for mass distribution. Although they managed to reach the lab and barricaded the entrances, several lizard-ized agents are teleported inside via Cloak's teleportation ability. As a result, Fitz and Simmons are quickly bitten and turned into lizards as well. In their lizard-ized state, they damage the equipment and attack Spider-Man before he webs them down. Spider-Man is able to cure the pair and everyone else in the building by using their aerosol dispersal unit to distribute the cure through the ventilation system. Once they are reverted back to their normal selves, Fitz and Simmons complain that their skin and tongue feel and taste like sandpaper, respectively. Dr. Connors assures them that the side-affect will only last a week.


Fitz's and Simmons's physical appearances are modeled to resemble their respective actors, Iain De Caestecker and Elizabeth Henstridge, from Marvel's Agents of S.H.I.E.L.D., and they sport similar clothing that they wore in the show's pilot episode.

Fitz is a Scottish young man with as muscular build, curly brown hair, and light brown eyes (contrasting Caestecker's blue eyes). He wears a dark blue, long-sleeved sweater with white lining over a light blue collar shirt and gray pants. He also wears a tie with a dark-and-light gray pattern and black shoes.

Simmons is an English young woman with shoulder-length, dirty-blond hair, and light brown eyes. She wears a dark blue, buttoned-up shirt under a light gray, long-sleeved blazer with red lining on the front and hem, and gray pants. She also wears a pair of silver stud earrings and red-and-white sneakers.


"I only have one vial of the cure. Please tell me you have a chemical synthesizer."
"What, do you think we're amateurs? Of course we do.
—Spider-Man and Fitz, on possessing a chemical synthesizer.[src]

Gifted with a genius-level intellect, Fitz and Simmons are considered two of the best technicians in S.H.I.E.L.D., and take pride in their work. Fitz seems to have taken slight offense when Spider-Man inquired if they have a chemical synthesizer in their lab, indicating he does not like being undermined in any way. As colleagues, the two are always seen together, and it is evident that they share a close bond. The pair is also share a similar personality: they are both intelligent, well-mannered, and possess a strong passion for science.

Abilities and Powers

"That's not a bomb just sitting on the table, is it?"
"Obviously, it's a prototype high-yield aerosol dispersal unit.
—Fitz and Spider-Man, the former telling the latter about the aerosol dispersal unit.[src]
  • Genius-level intellect: Fitz and Simmons possess a genius-level intellect. Due to their technological expertise, they are transferred and assigned to assist with repairing and upgrading the Triskelion.
  • Master Scientists/Engineers/Technicians: According to Spider-Man, Fitz and Simmons are reputed to be two of the best technicians in S.H.I.E.L.D., as they are tasked with reconstructing the Triskelion after being destroyed. They possess skills in engineering, as they helped upgrade the robots used in training sessions for S.H.I.E.L.D., and developed other scientific equipment for the agency, such as an aerosol dispersal unit. They also seem knowledgeable in biochemistry, assisting Spider-Man with analyzing the chemical composition of the Lizard cure in order to mass produce the cure to save the Lizard and the other lizard-ized S.H.I.E.L.D. personnel.



  • Fitz and Simmons are the first original characters from Agents of S.H.I.E.L.D. to appear in an animated series, making their debut in the Ultimate Spider-Man series. They are also the first characters from the Agents of S.H.I.E.L.D. cast to make an animated appearance, aside from Phil Coulson.[1][2]


Season 4


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