Of previous episodes at all.
"Though it contains almost no material from previous episodes, the episode has the format of a clip show, parodying the genre and self-parodying many aspects of the show itself. Production of the episode required at least 70 new scenes, many of which were filmed during a day at Universal Studios away from the show's sets."
"Paradigms of Human Memory" is the twenty-first episode of the second season of the American comedy television series Community and the forty-sixth episode overall. It was originally broadcast on April 21, 2011, on NBC. It was written by Chris McKenna and directed by Tristram Shapeero. In the...
https://en.m.wikipedia.org/wiki/Paradigms_of_Human_Memory