My name is Professor Ian Duncan and I would like to rap for you. Drop a beat! My name is Ian Duncan and I'm here to say, I'm going to rap to the beat in a rapping way! I've got a real big penis and I drink lots of tea...
— Professor Duncan
John Oliver as Dr. Ian Duncan
Dr. Ian Duncan (portrayed by actor/comedian John Oliver) is a psychology professor at Greendale Community College. Ian was born in Birmingham, England and grew up on 52nd street in the Islington district of London. His mother was a native of Lincolnshire from a town called Scunthorpe where she worked as a whore at a Stansbury pub with her thumbless sister. Duncan's father was absent for much of his childhood, a fact which haunts him to this day. It is alluded to that he left England after his parents divorced and came to America with his grandfather when he was very young. He eventually became a psychologist and settled down in Colorado where he was hired by Greendale's psychology department. Duncan started drinking heavily and his addiction caused him to run into some legal problems. At one point after driving drunk he tried to order a chalupa from an emergency call box on a highway. Jeff Winger at the time was still a practicing attorney and managed to get Ian off the hook. The two became drinking buddies and years later when Jeff enrolled at Greendale he unsuccessfully tried to call upon the favor Ian owed him. Although Duncan was present during Jeff's first and second year at school, he took a leave of absence before his friend graduated. He spent that time back in England taking care of his mother who was ill. Duncan returned to his position at Greendale a few years later and reconnected with Jeff who had since became a member of the faculty.
Despite his achievements Duncan appears to be very lonely. Perhaps as a consequence of this, he has developed an on-again, off-again drinking problem ("Pascal's Triangle Revisited"). He is indiscreet about his addiction frequently showing up to his classes inebriated ("The Psychology of Letting Go") and often outright telling students and faculty his condition. While he at times lectures Jeff on his ethical choices ("Pilot") he contradictorily makes a few ambiguous decisions himself. This includes attempting to exploit Abed's mental breakdown for a book deal ("Abed's Uncontrollable Christmas") or taking an Anthropology class he is substituting for and turning it into a BYOB party ("Applied Anthropology and Culinary Arts")
In 2009, Duncan was surprised to see his former lawyer and drinking Buddy Jeff Winger after He uses several students, notably Troy Barnes and Abed Nadir, to help prove "The Duncan Principle" which posited that the longer a subject was left in a waiting room, the more dramatic the person's subsequent breakdown would be. Duncan was assigned to give a year's worth of therapy sessions to Britta Perry after she was caught cheating on her Spanish exam. Throughout the year he has an antagonistic relationship with Ben Chang. Their feud came to a head during the transfer dance. Duncan was drunk again and insulted the Dean which led to an immediate suspension. Chang at that point had been fired due to falsified credentials and enrolled himself at Greendale to earn a legit teaching degree. Duncan had mocked earlier for his situation but Chang couldn't retaliate physically or he could be kicked out of school. Once Ian was suspended, Chang took advantage of that fact to hit him in the face with a roll of quarters.
In the study groups second year at a Greendale, Duncan is reinstated and finds himself unexpectedly teaching Anthropology. He is forced to take over the class they after the original teacher, Professor June Bauer is forced to go sabbatical after attacking a student. Because he knows nothing about the subject his teaching style was limited to showing the class various YouTube videos and assigning them dozens of dioramas to create. At Christmas time, Abed has a mental break down and Duncan is called in to try and therapize him. During the semester, he exploits the restraining order he put on Ben Chang, played piano for the Study Group when they briefly replaced the Glee Club who died in a bus accident, and watched a (European) football game at Jeff's apartment on Valentines Day. For a brief time he was sober but quickly fell off the wagon by the end of the year.
Professor Duncan is not seen during the 2011-2012 semester at Greendale but a book he authored is seen shown being held by Britta Perry who declared her major to be Psychology ("Contemporary Impressionists").
In the study groups fourth year ts school, Professor Duncan didn't make an appearance. However, he is mentioned twice on two different occasions. When the group takes a hot air balloon ride that goes horribly wrong, Troy suddenly asks if anyone's noticed how long it's been since they've seen Duncan ("Intro to Felt Surrogacy"). Towards the end of the school year, the study group flashes back to their time before attending Greendale. Jeff recalls how after being disbarred he was inspired to go back and earn a legit degree after encountering Chang. He had been handing out fliers for the school and Jeff asked him if his old client Ian Duncan still worked there. Chang told Jeff that Duncan had tenure there while also referring to him as a "drunken limey" ("Heroic Origins").
Ian Duncan returns to Greendale after some time away and joins the Save Greendale Committee. He reveals his absence was due to having to go back to England to take care of his sick mother. Upon his return he joins the investigation into the campus assailant called the "Ass a Crack Bandit". He creates a useless psychological profile on the perpetrator and ends up becoming one of the bandits victims. When Abed hosts a campus wide game of Hot Lava, Duncan participates hoping to win the $50,000 prize. He ends up being eliminated by Jeff and Annie when he tries to take Britta out of the game. Duncan and the Save Greendale Committee come up with a theme for the mid term dance. He later asks Jeff's help in trying to woo Britta. He decides to not take advantage of a depressed Britta and hangs out with Jeff instead. When Jeff accidentally ends up in a coma he imagines Duncan as the cartoon character of "Xim Xam" in his G.I. Joe fantasy. Duncan and the committee celebrate prematurely after a city inspector gives Greendale a positive assessment. School board members Carl and Richie prepare to sell the school to the Subway corporation. Most of the staff, including Duncan, is laid off to make way for the new Subway employees. Buzz Hickey and Duncan commiserate over their unemployment and find they have a few things in common. Duncan meets up with the committee in a last ditch effort to prevent the sale of the school. They learn of a map which leads to a hidden computer lab which may hold the school founder Russell Borchert's lost wealth. While searching for the entrance way to the lab, Duncan electrocutes himself after grabbing exposed wires. He suffered some post traumatic confusion but later regained enough of his senses to celebrate with the rest committee after they succeed in saving the school.
At Greendale, he considers himself solely responsible for the success of the campus "Green Initiative," in which the faculty lounge in the human sciences building was painted a calming shade of green instead of the previous shade of beige. ("[]")
Ian loves making fruit smoothies and going on bike rides. ("[]")
Seen on a recurring basis in Season One and Season Two, Dr. Duncan didn't appear in Season Three or Four and was only briefly referenced in with his name appearing on the cover of a psychology text Britta had, and later Troy wondering aloud why they hadn't seen him in a while.