- "Eh, you're just a droid. You don't know about real duty, about what it's like to have a brother."
"I am sorry. I have always wanted to have human feelings. But I do not. Goodbye"
- ―Fives and AZ-3 meet on Kamino
- "Might I suggest a second brain scan? An atomic-level brain scan."
"This is unnecessary. The phase one and two scans we did are sufficient. He is too weak for a phase five atomic-level scan."
"I calculate the beneficial knowledge we could gain from a phase five atomic scan is worth the risk."
"The only way to discover what has happened to this clone is to terminate him and do a full-scale autopsy on the molecular level."
- ―AZ-3 and Nala Se discuss Tup's condition
In 20 BBY, Clone Trooper Tup was brought to the medical labs on Kamino for extensive examination to discover why he unconsciously killed Jedi General Tiplar during the battle of Ringo Vinda. AZ-3 worked with Kaminoan doctor Nala Se, Jedi Master Shaak Ti and other medical droids in the analysis of Tup and his comrade, ARC Trooper Fives, who was possibly exposed to the same ailment that affected Tup. AZ-3 examined both troopers, performing hypertests on Tup and minor scans on Fives, finding that the latter had no apparent symptoms. However, he was forced to keep the trooper quarantined in a room adjacent to Tup's.
When he returned to Se and Ti, Tup's condition began to deteriorate. Ti believed that he was suffering from a mental sickness, possibly induced by Separatist brainwashing. AZ-3 suggested that they perform an atomic-level brainscan to pinpoint the exact problem, but Se claimed that the scan could damage his neural tissue and even kill him. Instead, she wanted to terminate Tup and perform a molecular-level autopsy. When Ti objected to her notion, reminding her that the Jedi were equally responsible for the Clones' care, Se permitted her to advise the Jedi Council while she spoke with Prime Minister, Lama Su.
AZ-3 returned to Fives and informed him of the situation. Fives insisted that they perform the phase five brain scan regardless of Se's input. AZ-3 first thought himself incapable of defying orders, as per his programming, but Fives reminded him that it was also his programming to give the utmost care for the patient and allowing the patient to be terminated would be against his protocol. Under this rationale, AZ-3 and Fives went into Tup's room and performed the atomic scan, revealing a tumor within Tup's brain that blocked neural impulses from communicating. Before they could analyze it, however, Nala Se returned to the room.
Though she did not see Fives, she discovered that AZ-3 had performed the brain scan without her consent and ordered him out of the examination. She still planned to terminate Tup and perform the autopsy as planned. Fives quickly had AZ-3 hack into the medical center's mainframe and trigger an intruder alert to draw her out of the room so that he and AZ-3 could further examine the tumor. Upon its removal, Se returned and attempted to confiscate it, but Fives refused to trust her. Shaak Ti then arrived with a security escort and stabilized the situation. At that moment, Tup regained consciousness and spoke to Fives, claiming to have found freedom from his "mission", before passing away.
Following Tup's death, AZ-3 was scheduled to have his memory erased to keep the incident completely confidential. While being escorted through a hallway, he passed Fives, who was on his way to a physical check before he returned to the front lines. However, AZ-3 informed him that he too would have his mind wiped and be reassigned to Kamino sanitation detail. Upon learning this, Fives subdued their respective security escorts and took AZ-3 back to his room. They found that Nala Se had not passed the tumor extracted from Tup on to Shaak Ti per the Jedi's request and gave it to AZ-3 to carry.
Fives launched a Kaminoan flight pod as a distraction for Kamino security so that they could return and investigate the tumor's origin. AZ-3 initiated one of his various survival modes, allowing Fives to ride him as a small speeder, to reenter Tipoca City undetected. When they arrived, he lured a Clone Trooper into the storage room where Fives ambushed him so the latter could use his armor as a disguise. From there, they went to the Genetic Records Hall to search the Jango Fett genotype for any history of tumors. However, they discovered that the sample taken from Tup not only matched nothing within Fett's genes, but it was also foreign to the body, implanted in the brain at the embryonic stage.
Fives suddenly noticed that the other Kaminoans in the room were quickly filing out and AZ-3 led him to an emergency access hatch through which they escape then security forces arrived. Making their way through the series of service tunnels, AZ-3 and Fives discussed possibilities of the biochip's purpose for being in Tup's brain, leading Fives to request his companion to operate on him and check if there was a biochip within his mind too.
AZ-3 brought him to a sterile facility where he sedated him and extracted a biochip similar to Tup's, the difference being that the one found in Tup had somehow decayed―causing his madness―while Fives's seemed healthy. Fives then wanted to check Clone hatcheries to see how many others were implanted. On their way to the lab, they passed through a training area, which aroused the suspicion of a few Kaminoan scientists. At the hatcheries, AZ-3 compared several embryo jars to Fives's chip and found that all Clone embryos past stage three development were implanted. Just then, Nala Se confronted them, telling them that the biochips were harmless inhibitor chips to hinder the Clones' inherent aggression, implanted at Jedi Master Sifo-Dyas's behest.
Shaak Ti also entered with a security force and ordered Fives to stand down. AZ-3 showed Ti both inhibitor chips, comparing them in structure and overall health. Fives pleaded that more incidents like Tup's could arise and undermine the entire Grand Army of the Republic. Despite Se's request to terminate Fives, Ti decided to allow him to make his case directly to Supreme Chancellor Palpatine on Coruscant.
- The online episode guides of StarWars.com spell his name with an I, calling him "AZI-3". This is presumably an error as he is only referred to as "AZ-3" in the episodes themselves.
- AZ-3 is voiced by Ben Diskin, who also provided the voices of Morley and WAC-47 earlier in the show.