Arrow's 150th episode, "Emerald Archer," featured a number of surprising cameo appearances from past characters. Some were made by former members of Arrow's sizable cast, who left the show in earlier seasons. Other appearances were made by characters who went on to headline their own Arrowverse series.
Part of the 150th episode was devoted to showing portions of a fictional documentary called Emerald Archer: The Hood and the Rise of Vigilantism. Focused upon Oliver Queen and how Star City responded to increasing crime in the wake of its anti-vigilante laws by deputizing its superheroes, most of Arrow season 7's cast were interviewed as part of the documentary. Yet other characters from the previous seasons of Arrow were brought in to give their own opinions on whether or not costumed crime-fighters are necessary.
This breakdown will run through all of the Arrow characters that are no longer part of the core ensemble that are seen or referred to over the course of the Emerald Archer documentary. Some are familiar faces that are fondly remembered by Arrow-heads to this day. Other characters are decidedly obscure and just vanished from the series with little explanation.
The Emerald Archer documentary in the "Emerald Archer" episode opens with archival footage of Quentin Lance from the year 2014. Over the course of Arrow's first six seasons, Quentin Lance was both the Sheriff of Nottingham to Oliver Queen's Robin Hood and one of his most stalwart allies in the battle to save Star City. He was a police detective, a beat cop, the chief of police, and finally Oliver's deputy mayor. He also became a second father to both Oliver and Thea Queen and the example of everything a father should be to his children, according to Oliver. He died from complications during surgery in the Arrow season 6 finale, after taking a bullet meant for Black Siren.
Thea Queen appears in Emerald Archer, speaking about how if it hadn't been for vigilantes, the people responsible for killing her mother and half-brother, Tommy Merlyn, wouldn't have been caught. Oliver's younger sister had perhaps the most widely varied backstory of any character in Arrow's history. A wild party girl who loved booze and pills as the series opened, she would later learn that she was the product of an affair between Moira Queen and Malcolm Merlyn.
Her biological father took her under his wing for several months, between Arrow season 2 and season 3, spiriting her away to the nation of Corto Maltese, where he began training her in the arts of the assassin while brainwashing her into a tool to use against his enemies. Thea later broke her programming, learned that her older half-brother was the vigilante called the Arrow, and joined him as the hero Speedy in Arrow season 4. Turning her life around, she became a successful club owner and served as Oliver's chief of staff during his time as mayor, before leaving Star City in the Arrow season 6 episode "The Thanatos Guild" to destroy all the Lazarus Pits that Merlyn had uncovered.
The younger of the two Lance sisters, Sara Lance is briefly interviewed in Emerald Archer about her father's death. Sara's life forever changed when she stowed away on-board The Queen's Gambit to enjoy a wild weekend with her sister's boyfriend, Oliver Queen. Presumed lost at sea for six years after the ship was sabotaged by Malcolm Merlyn, Sara would go on to spend "five years in Hell" to rival Oliver's exile from Star City.
After being rescued by the mad scientist Dr. Anthony Ivo and spending two years on his ship, The Amazo, and nearly dying at the hands of Slade Wilson on Lian Yu, Sara was found by the League of Assassins and adopted into the clan. She was given the name Canary for her musical laugh and formed a romantic relationship with Nyssa Al Ghul, daughter of Ra's Al Ghul. Sara returned to Star City after being given the rare privilege to leave the service of the League of Assassins and fought Slade Wilson again after he took on the identity of Deathstroke. Killed by a brainwashed Thea Queen, Sara was resurrected with the assistance of the warlock John Constantine and went on to be recruited into the Legends of Tomorrow, whom she now leads as White Canary.
Cindy "Sin" Simone
Addressed only by her street nickname of Sin, Cindy Simone was a confidant of both Roy Harper and Sara Lance during Arrow season 2. She appears in Emerald Archer, talking about how she knew the Arrow and Canary "back in the day" and how they saved her life more than once. Sin was the daughter of a man who died after his plane crashed on Lian Yu. Sara promised the dying man that she would watch over his daughter if she ever got back to civilization. Sin was last seen in the Arrow season 3 episode "Uprising," where she confirmed to Quentin Lance that Arrow's new Canary seen running around Star City was not Sara Lance.