Continuity mistake: Britta points out that Pierce keeps his dad's bow tie on his night stand. A few moments later, after Jeff finishes opening up and walks away, the bow tie on the night stand has disappeared.
Conventions of Space and Time - S4-E3
Continuity mistake: Annie splashes Jeff in the face with a drink and she asks for two more, with Jeff still having water dripping on his face. He shouts "enough!" and suddenly his face is much drier in the next shot.
Alternative History of the German Invasion - S4-E4
Continuity mistake: During the podcast scene at the credits, Karl is gripping a trident with both hands. After asking if it was an apology, the camera cuts to Abed and he is now holding it with only one hand. (00:20:50)
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.
Alternative History of the German Invasion - S4-E4
Continuity mistake: Reinhold and his two friends are walking out of the administration building around the study group. Reinhold makes it out of the door with his two buddies close behind. In the next shot, they have all suddenly exited the room.
Advanced Documentary Filmmaking - S4-E6
Continuity mistake: When the group is making posters for the MacGuffin Institute meeting, Annie holds up a poster saying "Welcome Archie" to show off name brand glitter but the character of Archie isn't introduced until the next episode (in which the banner shows up again). (00:03:11)
Suggested correction: This isn't a mistake. The episodes were simply aired out of order than the order they were produced. "Economics of Marine Biology" (production code 406), the following episode, was filmed before "Advanced Documentary Filmmaking" (production code 408).
Advanced Documentary Filmmaking - S4-E6
Continuity mistake: Abed is making a documentary, and we see the fact that there are two cameras throughout the episode, so they are definitely acknowledged. However, in the scene at the trout fisherman's house, there is someone filming behind Annie and Troy and towards Annie and Troy. The problem being that whenever it shows Annie and Troy in front, there is no cameraman behind them, but when it cuts to behind them again there is somebody there filming.
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)
Advanced Introduction to Finality - S4-E13
Continuity mistake: In episode 11 of Season 4, it was stated that Leonard got an A in 1968, then opted for pass/fail to have the highest GPA in the college. In the final scene of this episode, however, it shows Greendale college as being established in 1974.
