- "This was not the work of religion. It was arrogance. It was hypocrisy. It was hate. Those horrible men who hijacked those planes hijacked my religion that day, too. They insulted my God. So no, this isn’t too difficult. It’s a privilege to be able to serve this victim, to show him the care and love that was so absent that day."
Originating from Iran, he is a devout Muslim and prays five times a day. Expecting others would find it odd that he is both a scientist and very religious (a suspicion his co-workers later confirmed), Vaziri decides to put on a false accent to sound "fresh off the boat" and thus make his religious devotion seem like an irrelevant byproduct of his heritage.
In Beautiful Day in the Neighborhood, he slips up, and his secret is revealed first to Dr. Saroyan, and then to the rest of the team (and the audience). When asked if she noticed anything strange about Arastoo's accent, Brennan says she thought it was odd that an Iranian would speak English with a Jordanian accent, but she felt that was his business. Dr. Sweets helps Arastoo work through these issues.
In The Devil in the Details, Vaziri says he served as a military translator in Iraq, where he killed an insurgent while defending his life after surviving an IED. His fellow passengers did not survive.
In the fourth-season finale, Arastoo was re-imagined as a potential buyer of Booth and Brennan's night club.
Arastoo shows a high level of proficiency with nunchaku whilst assisting Hodgins in an experiment, and in his first appearance speaks of the 'quips' he endured from "the First Battalion, 9th Marine Regiment, Regimental Combat Team One" in a manner which suggests that he himself was a member.
In the sixth-season premiere it is revealed he switched majors from Forensic to Cultural Anthropology and is interning at the Baghdad Museum. He returned in The Bones that Weren't.
In "The Pinocchio in the Planter", Wendell mentions that Arastoo comes from a wealthy family.
He played a fairly major emotional role in the season 8 episode 6 "The Patriot in Purgatory". He made a speech on the 9/11 terrorists' religion and his own while investigating the death of Tim Murphy.
Arastoo is often in investing the victim with humanity at all stages, and feeling empathy for their plight, as in "The Survivor in the Soap" or "The Signs in the Silence" (Which saw the team deal with 'live' evidence in the form of teenage abuse victim Amy Shenfield, Arastoo being particularly moved when X-rays revealed the extent of abuse Amy had been subjected to).
In The Bod in the Pod it is discovered that he writes poetry in Farsi and at least one of the poems is dedicated to Cam. At the end of that episode we also find out they started seeing each other some time shortly prior.
In the same episode, Arastoo admits to Hodgins that he is a political exile and can never go home again. In 1997 while in his first year of university, Arastoo had published his poems on an underground press, believing the Khatami regime to be more accepting of them. Being eighteen, his poems were about love, freedom, sex and democracy. However, it was considered unacceptable and Arastoo was forced to flee the country before an edict was issued for his arrest. Hodgins admits to finding the idea of Arastoo being a political exile to be cool.
In The Pathos in the Pathogens, Arastoo attempts to lift a skeleton and a sharp tool injected in the humerus of the victim stabs his finger, infecting him with what was thought to be a modified CHIKV virus that can not be properly identified by the CDC. Arastoo continues to lose health until it was found that he was not infected with a modified virus, but a modified bacterium, Clostridium botulinum, that produces a powerful neurotoxin. The team finally finagles the antiserum from Simatech's Dr. Thorne when Brennan takes action into her own hands and saves Arastoo.
In "The Murder in the Middle East", after returning to Iran to look after his sick brother, Arastoo is kidnapped by a powerful Iranian politician who threatens to imprison Arastoo to get Arastoo to help the man solve the murder of his son Darius in secret. Cam and Booth fly to Iran and negotiate a deal where they will use their resources to help solve in the murder in exchange for the release of Arastoo once the case is over. Though the man eventually wants to stop the investigation because he disapproves of his son's lifestyle, Arastoo and Cam get him to change his mind. The team eventually identifies the killer as the Darius' boss who he had discovered was committing embezzlement. Though Darius' father still disapproves of his son's actions as it goes against their religion, he mourns him as he loves his son which Cam and Arastoo helped him see was important. Before leaving Iran, Arastoo takes Cam to meet his brother for the first time.
In "The Brother in the Basement", Arastoo breaks up with Cam and leaves the Jeffersonian to try to look for a new job as a forensic anthropologist. He returns in "The Doom in the Boom" when he heard that Cam was near an explosion at a crime scene. He was offered a position in Berlin, but after realizing that it was a mistake for him to leave Cam, he declines as was revealed in "The Monster in the Closet". Cam, who is seeing Sebastian Kohl at the time, declines his offer. In "The Movie in the Making", Arastoo reveals that he wants to be a husband and a father. Cam, who was standing behind him, overheard him talking in the Bone Room and proposes to him, to which he accepts without hesitation. The two married in the penultimate episode of the series, "The Day in the Life", Cam contemplating taking time off from her role as head of the Jeffersonian to go on a honeymoon.
In "The End in the End", both Cam and Arastoo make it out of the Jeffersonian safely before the explosion. After Brennan can't remember the clue she found to Mark Kovac's location in Fred Walden's bones nor can she analyze them due to her head injury, Arastoo joins Clark Edison, Wendell Bray, Daisy Wick and Jessica Warren in performing an analysis on their own to find the clue. After a rousing speech from Hodgins, the intern team is able to use what Brennan has taught them to find the clue and through it, locate Kovac. Afterwards, Cam reveals to Hodgins and Brennan that she and Arastoo are taking a leave of absence during which Hodgins will be in charge in order to travel to Mississippi and adopt three foster children there.
- What is not explained is why Vaziri, from Iran, would serve as an interpreter in Iraq. Iranians speak Persian, whereas Iraqis speak Arabic, although it is possible he is trilingual. It is unclear if the writers meant Afghanistan (where Persian would have still been of use as they speak a Persian-related Dari or Pashto), or if the writers are retconning Vaziri as a speaker of Arabic rather than a Persian. It's quite possible that Arastoo is multi-lingual, speaking Persian, Arabic, and English. While the language spoken at home while he was growing up would most likely have been Persian or English, as a devout Muslim he would probably have some knowledge of Arabic anyhow and it is entirely possible that he studied Arabic academically.
- Arastoo is an avid fan of baseball and basketball, as evidenced by his conversations with Hodgins and Cam.
- He was a State All-Star baseball player in high school, and was even being recruited by farm teams. At the time of the show, he played on a team with his mosque against churches and synagogues, even going so far as to invite Hodgins to join.
- He was a hot-head as a teenager, to a degree that he believed his parents still considered him as one decades later.
- The name "Arastoo" is the Persian form of Aristole.