Character mistake: Annie when giving her gifts is holding two little mini flags to cover the possible ethnicity of Shirley's baby. One is a Chinese flag and the other is Zimbabwe. Annie makes reference to the fact that the ethnic food she made is one from Ghana. She makes Ghana ethnic food but does not get the right flag for Ghana. She decorates the table with numerous flags which are also Zimbabwe.
Visible crew/equipment: At the beginning of the episode, after Pierce rejoins the group and Jeff and the others begin to leave the room, watch Britta as she stands up. When she turns away from the camera, you can see the actress' microphone-pack in the back of her jeans briefly. (It's hard to spot but it's there, and is confirmed in the commentary track.).
Other mistake: During Leonard's "Let's Potato Chips" YouTube video during the ending credits, you can see the video reaches the end of the load/play bar (watch the circle), yet the video continues for several seconds. Once the circle reaches the end of the load/play bar, the video is over and won't continue.
Visible crew/equipment: When Jeff runs to the car which his father drives and opens the door of the driver, you can see the camera in the side window of the car. You can see it's a set camera and not a 'handheld type', the one that Abed is using during this episode.
Visible crew/equipment: After Britta accidentally bumps the gurney into the window, she grabs the body bag in a failed attempt to keep the corpse from falling out into the quad. Right as she grabs the body bag, look on the ground behind her. Someone slides a mat in behind her for her to fall onto.
Continuity mistake: Pierce tells the Biology teacher that the study group members are the only people he has told about having sex with Eartha Kitt in an airplane bathroom. However, in 3.04 'Remedial Chaos Theory', Pierce tells the group about Eartha Kitt for the first time. Also, in 3.03 Shirley calls Britta's lighter her "marijuana lighter", but she doesn't find out about Britta smoking weed until 3.04. These errors are due to 3.03 and 3.04 being aired out of order according to their production, and have been acknowledged and confirmed by creator Dan Harmon himself, but they still count as mistakes.
Continuity mistake: Near the end, when Jeff says to Troy "you're a man now" the camera goes onto Troy and we can see Abed asleep on Britta's shoulder (Britta is also asleep), even though in the shot before that, they were both awake. Then after the shot of Troy we see Britta and Abed awake again.
Revealing mistake: In the season one episode "Modern Warfare", when Chang's paint bomb explodes, pay attention to the background. You will see paint exploding from three different points on the ground. (One to the center, one to the left and one to the right) The only problem is that there was only one paint bomb in the center, so it makes no sense that there are 3 explosions from different points.
Character mistake: Season 3 Episode 9 - "Foosball and Nocturnal Vigilantism": In the bonus clip where we see Leonard's online video about frozen food, the first thing he says is, "This is November 29th". However, if you look under the video, you can see the video was uploaded on Nov 26, 2011, which is three days earlier.