Mr. Stone is a mysterious, seemingly emotionless man that the study group encounters after Pierce Hawthorne's passing. Mr. Stone has a dangerous accusation, a tantalizing offer and a devious plan that will change the group forever. Mr. Stone's first appearance is in the Season Five episode "Cooperative Polygraphy". He is portrayed by actor Walter Goggins.
In the study group's fifth year at Greendale together, the gang is in mourning over Pierce Hawthorne's death. Shortly after attending his funeral, they were approached in Group Study Room F by a man who introduced himself as Mr.Stone. He explained that per the instructions of Pierce's will he was to carry out an inquest into Hawthorne's death. He told them they would be hooked up to lie detectors as his team of polygraph technicians set up their equipment. Chang, who had dropped by to see how the group was coping, mocked their predicament. He was about to leave when Stone informed him that he was on the list and his presence was asked for as well.
Even though it's strictly voluntary, they all decide to participate to honor Pierces last request. Once they got hooked up to the lie detector machine, Stone begins his first round of questions. Stone asked Britta about any sexual fantasies she had about Pierce, Jeff's sexual orientation was questioned and Shirley's donations to a pro choice political group is brought up. Stone turns to Troy and asks him if Pierce telling him Fat Albert died from diabetes angered him enough to want to murder him. Stone then inquires about a special doomsday plan he and Abed had in case of a zombie apocalypse which didn't include anyone else in the study group. Chang was eager to be questioned as well declaring he had nothing to hide.
Stone then asks him if he ever masterbated in the study room. In response Chang removed the polygraph sensors and left. Stone turned to Abed and if he ever "911"-ed anyone. He followed that up by asking if as a child he ever developed any homicidal tendencies after accidentally killing a small animal. Annie and Shirley are relieved when he says "No" and the polygraph techs confirmed he was telling the truth. Stone asked him if he was still using Jeff's Netflix account without his permission. He then asked Annie if she used her exceptional intelligence and organizational skills to plot Pierces murder. Stone then got Annie to admit she overcharges Troy and Abed for their share of the rent.
The series of revelations caused a huge argument to break out amongst the group. As the bickering continued, Stone sat down in Pierces seat at the study table. He yelled for the study group to stop arguing and explained the first round of questions was just to calibrate the equipment. The real interrogation was about to begin.