When Dean Pelton begins checking class schedules, he discovers that Jeff has listed a class that doesn't exist. Just when it appears Jeff will be caught in a lie, the mysterious "Professor Professorson" emerges from the shadows to confirm that Jeff has been taking his class, "Conspiracy Theories in U.S. History," at night school. When Jeff later admits to Annie that he's never seen Professor Professorson in his life, the two decide to find out who the professor really is. Meanwhile, Abed and Troy are busy building the most elaborate blanket fort that Greendale Community College has ever seen.

Source: NBC