When the group chases Garrity through the blanket fort, they get held up by a Latvian Independence Day parade. The original air date was November 18, 2010 which actually was Latvian Independence Day.
Pierce doesn't have a single line of dialogue in the episode.
In Basic Rocket Science (2010), Britta mentions that Greendale has a course in Theoretical Phys Ed. Here, the class turns up on Garrity's list of fake courses.
Two episodes ago, in Abed's Robovision, one of his memos was "build blanket fort"
The Greendale Community College Student Course Schedule printed by Dean Pelton contains the following information: Student Name: Winger, Jeffrey / Student ID #: 32269432