Gemma was one of the captive phenoms in 'Alphabet Soup' along with her twin brother, Gem. Both speak in conjoined sentences with a high level of energy. They attempted to befriend the solitary Dr. K and even gave her a birthday present, even though they knew, she didn't like them. She and her brother were the original testers for the prototype ranger gear for Project Ranger. Later on, Dr. K discovered that they were being deceived into staying in the Alphabet Soup facility, and she had tried to get them out of the facility only to face dire consequences. When Venjix gets past Alphabet Soup and seeped into the world, she and her brother help Dr. K get out of the facility. She was last seen with her brother running off to collect the classified Gold and Silver series bio-suits before a section of Alphabet Soup collapsed behind them, but an explosion seemingly killed them in front of Dr.K.
Mysterious Gold and Silver Rangers later appeared twice to save the core Rangers from Venjix's new body. Afterward, they all returned to Corinth, it is within the city that it is confirmed that Gem and Gemma are indeed the mysterious rangers, and the two are subsequently reunited with an excited teary-eyed Dr. K.
Their Rangers suits, being experimental at the time they were created, do not have the same properties that the other Rangers do. For instance, they cannot manipulate their biospheres like the other five, and the suits themselves have a pilot's jumpsuit design to fit their aircraft Zord design. This includes their wing-like cuffs on the suit which, unlike the wheel or gear (in the case of Green and Black) cuff design on the others, does not spin. Gemma has the series 8 Engine Cell Chip used for the Tiger Jet and Whale Zord. Though numbered '8', she is the seventh member of the team. She is numbered this because her zord is numbered 8 hence her current number.
Before reuniting with Dr. K and meeting the Rangers, Gem and Gemma were out in the wasteland on an offensive campaign against Venjix. Because they were out on this campaign for so long, they have a "shoot first, ask questions later" type strategy, which greatly disturbs the more passive Colonel Truman, as well as earns them the nickname "The Boom Twins" by the other Rangers. This makes them trigger-happy, and they take very little time to plan, but more than make up for it with their fighting skills. The twins rarely separate from one another, and it often seems as though they share the same brain, or at least think very similarly, since they always end up finishing each other's sentences, but there have been times where they have had their own individual thoughts. At some point during their time on the run, they were forced to work in a Grinder-building factory, at which point they met a blind girl they would later learn was Dillon's sister.
After the war, Gem and Gemma join Eagle Squadron, now under Scott's leadership, obviously recommended for the posting because of their experience with their aircraft Zords. They seem to be quite excited about their new posting, saying that they "get to blow things up, and get paid for it."
While the both of them act relatively simple-mindedly and childishly, Gemma and her brother have a genius IQ possibly equal to that of Dr. K as they can easily understand quantum mechanics. After spending her time with the other Rangers, they eventually grew closer to them and work with the team, rather than just each other, even managing to restrain themselves from simply blowing things up until its necessary.
AbilityThe Cloud Hatchet is the Ranger Operators Gold and Silver's primary weapon. With it, one can perform attacks such as to freeze, to fire lasers, create fire or fly. It can combine with the Sky Morpher to form the SkyShift Blazer.
Attacks are done by activating numbers using the switches. Pressing a single numbered switch activates an attack, while pressing two or three unleashes other attacks.
- Gemma's counterpart from Engine Sentai Go-onger, the Super Sentai series RPM was based on, was Miu Sutou.