CT-5555 - better known as "Fives" - was a supporting character in Star Wars: The Clone Wars. He was a clone trooper in the Grand Army of the Republic and a member of the 501st Legion under the command of Jedi General Anakin Skywalker. He made numerous appearances between Seasons 1 and 6, taking part in several key battles in the Clone Wars. Like all clone troopers, he was voiced by Dee Bradley Baker.
In 19 BBY, Fives took part in the Republic's invasion of Ringo Vinda. During the campaign, his fellow clone soldier and best friend Tup went missing for five planetary rotations before appearing once again and returning to the front line. As the 501st Legion advanced across the Ringo Vinda space station, Tup suddenly began to experience headaches and dizziness. He later fell into a trance-like state, muttering the words "Good soldiers follow orders" as he raised a blaster to Jedi General Tiplar and fatally shot her. Because of this action, the Republic army lost its momentum and was forced to fall back.
Later, Tup underwent a medical examination, but his test results determined that he was perfectly healthy even as his mental stability continued to deteriorate. It was decided that Tup needed to be taken back to Kamino so that the scientists responsible for engineering the clones could determine what was wrong with him. Fives accompanied him to Kamino with Skywalker's permission.
On Kamino, Dr. Nala Se determined that Tup was most likely carrying some manner of virus, explaining that she would need to terminate Tup in order to properly ascertain the nature of the infection and develop a defence against it to protect the other clones. However, Fives believed that something was amiss and, against orders, decided to look into the issue himself. Assisted by the medical droid AZI-3, Fives managed to distract Dr. Se long enough to move Tup into another room and conduct an atomic scan on him. The scan revealed what appeared to be a tumor on Tup's brain, and so AZI-3 performed a quick surgical procedure to remove it. Tup died shortly after the tumor was removed, but in his final moments he stated that he was finally "free of the never-ending mission in their nightmares".
Following Tup's death, Dr. Se took the extracted tumor, intending to have it sent to a medical facility on Coruscant for analysis. However, Fives did not trust the doctor and found out that she was planning to erase his memory and have AZI-3 reprogrammed. Determined to get to the bottom of the mystery, Fives once again enlisted AZI's help. They snuck into the primary cloning facility and conducted an analysis on the embryos of one of the breeding trees, detecting that all of the clones possessed the same tumor Tup had. AZI determined that the tumors were, in fact, organic chips that were implanted into the clones' brains during development and served as a type of neural inhibitor. Every clone in the Republic Army had one, including Fives, though upon this discovery he had AZI remove his chip. When Dr. Se and Jedi Master Shaak Ti caught up to him, Fives had already had his chip removed. He told Shaak Ti about the biochips, but Dr. Se was quick to suggest that Fives might be malfunctioning as a result of his chip's removal.
In order to determine that Fives was still fit for service and to resolve the mystery surrounding the biochips, Fives was taken back to Coruscant. While in transit, Dr. Se injected Fives with a drug that clouded his mind. Supreme Chancellor Palpatine himself met with Fives along with Se and Shaak Ti. Despite his best efforts, Fives's description of his experiences were unable to convince any of the other members of the meeting of his belief of a conspiracy. Despite Se's insistence that Fives was suffering from paranoia and mental degradation, Palpatine requested to speak to the soldier alone to hear his story in further detail. After Shaak Ti and Nala Se had left, the Chancellor revealed the true purpose of the biochips to Fives as well as his involvement in the plot. He then attacked Fives, who in a moment of self-defense was framed as a potential assassin. Now a fugitive from justice, Fives fled into the bowels of Coruscant, looking for potential allies and anyone who might hear him out. Eventually, he arrived at the clone bar, 79's. There he managed to convince his longtime friend, fellow 501st soldier Kix, to contact Anakin Skywalker and Captain Rex so that they could speak privately.
To Fives's surprise, both Skywalker and Rex appeared at his requested meeting spot. Fearing that neither would listen to his story, he trapped both in a ray shield. Agitated by his experience and by Nala Se's drugging, Fives's attempts to explain his actions and his discoveries proved incoherent. When Skywalker accused Fives of trying to assassinate Palpatine, the tension escalated. Just then, midway through Fives's explanation, Commander Fox and a squad of Coruscant guards arrived to arrest him. Desperate not to be captured, a terrified Fives reached for one of Rex's discarded blasters. After a warning, Fox shot Fives in the heart. Fives spent his final moments in Rex's arms, where he spoke his last words, referencing Tup's, having finally found peace.