Alternative History of the German Invasion - S4-E4
Continuity mistake: When Malcolm McDowell is writing on the board early in the episode, he draws a line under the word "victors". In the next shot of the board, the line has moved, and the gap between the V and I is larger.
Continuity mistake: After Jeff and Britta have had sex, when Britta is pointing her gun at Jeff, in shots behind Jeff she is holding the gun sideways, but in shots from behind Britta she is holding it straight.
Continuity mistake: The study-room on the second floor of the library, right next to a set of stairs, and the area isn't particularly bright. In the rest of the series, the study room (which is meant to be the same study-room) is now located on the first floor of the library, nowhere near any visible stairs and the area is much brighter and more well-lit. As often happens, the pilot was filmed before any other episode, and the setting was changed in the meantime.
Contemporary American Poultry - S1-E21
Continuity mistake: At the end when Abed is talking to the Dean, there's an open to-go box with chicken fingers. After the Dean asks who would steal a box of hairnets, it cuts back to Abed and the box and ketchup are gone. Post-it notes are also now seen and the stapler moved. In the next shot of Abed, the chicken is back.
Romantic Expressionism - S1-E15
Continuity mistake: At the start of the dance, the Human Being and its partner can be seen dancing on the dance floor, but a few shots later they can be seen entering the room over Jeff's shoulder.
Continuity mistake: In the very first shot, we can see there's a man with a dark coat, sunglasses, short hair and earbuds standing directly in front of the dean. When it cuts to the opposite angle, he's no longer there. When it cuts back to the first angle a few shots later, he's suddenly back.
Asian Population Studies - S2-E12
Continuity mistake: Right after the intro, the group is sitting in the Anthropology class waiting for Prof. Duncan. The chalkboard is filed with writing on it. When Duncan enters, the chalkboard is, except for the 3 top-corner titles, completely clean. (00:03:02)
Grifting 101 - S6-E9
Continuity mistake: When the grifting professor and Jeff are speaking in their office after meeting each other, we see the bottle of alcohol change amounts as the camera moves angles (from Jeff's POV to the teacher's). It is lower when the teacher is all alone, and there's more when it's Jeff's POV. (00:20:14 - 00:20:36)
Continuity mistake: Britta has a cellphone in her right hand. The camera cuts to behind her and she's flailing her right hand with no phone in it. In the next shot, the phone has jumped to her left hand. (00:13:05)
Laws of Robotics & Party Rights - S6-E5
Continuity mistake: Jeff writes the word "Law" on the board and draws out his "born into dirt" story. A few cuts later, after Garrett asks him when he stopped being funny, the word "Law" looks much different, and the other parts look redrawn. (00:13:30)
Laws of Robotics & Party Rights - S6-E5
Continuity mistake: Jeff is facing Willy as Willy asks him where he was born. Still facing him, he responds, but before he finishes his sentence, the camera cuts and he is how facing completely away from Willy and is drawing on the chalkboard. (00:13:20)
Lawnmower Maintenance & Postnatal Care - S6-E2
Continuity mistake: Elroy is holding the Dean in virtual reality. In real life, his hand is in front of his face and slightly opened. When the camera cuts closer, his hand is lower and clenched in a tight fist. (00:21:00)
Lawnmower Maintenance & Postnatal Care - S6-E2
Continuity mistake: Britta is running out of her parents' house, leaving the door behind her closing. In the next shot, the door has stopped moving and is opened up more. (00:16:55)
Continuity mistake: Britta sets down a tray with a sandwich on it horizontally right in front of her. In the next shot, it has now moved further away from her and is sitting vertically. (00:12:05)
Continuity mistake: Chang's sunglasses are sitting on the table in front of Professor Hickey and Shirley. When Richie sits down, the sunglasses have disappeared. (00:10:10)
App Development and Condiments - S5-E8
Continuity mistake: Jeff is doing stand-up comedy with a mic stand an a stool with a bottle of water on it behind him. A few shots later, without touching them or anyone moving them, they all completely vanish. (00:12:55)
App Development and Condiments - S5-E8
Continuity mistake: There is a gavel with its handle facing inwards toward the table, facing away from Jeff. When the app developers begin their pitch, the handle of the gavel is now facing towards Jeff. (00:01:00)
Analysis of Cork-Based Networking - S5-E6
Continuity mistake: Abed opens his locker to reveal Britta's spoiler sheet. It rolls open but it doesn't fold open to see what it says exactly, but two shots later it is now open fully. (00:05:30)
Analysis of Cork-Based Networking - S5-E6
Continuity mistake: As Professor Hickey is waiting on the janitor to finish his meal, he looks away towards the hallway. After the janitor speaks, the camera cuts and he is now looking directly at him. (00:03:05)
Economics of Marine Biology - S4-E7
Continuity mistake: A barber is adjusting Jeff's collar when Pierce begins to talk about the country clubs he belongs to. In the next shot, there are no hands touching Jeff's collar and in the shot after that, his collar is completely covered by the barber's cape, with no barber behind him anymore. (00:20:30)
Answer: His attempt to "kill" Jeff was to roll at him as an iPad on a stick. He knew it wouldn't work, but it played to the story that he was a killer as he knew Jeff would tell people about it, or attempt to retaliate for it.