When Jeff draws on the chalkboard, he draws a line from the dirt to his name. He doesn't draw a complete circle around his name, yet the next time the board is seen the circle is complete.
In the opening scenes, when Frankie walks into the study room the robot is positioned between her chair and Chang's. When Chang gets up to look at it, it has moved over behind her chair. Seconds later it has moved back to its original position, before Chang appears on the screen and begins to control it.
After Britta and Abed talk by his locker, Abed closes the locker and walks away. A girl, a few lockers over, walks up and opens her locker, without entering the combination.