As the study group gathers to assemble their 20th and final Anthropology diorama of the year, they begin reminiscing about their favorite times together - including a trip they made to a western ghost town, a last minute glee club performance, the clandestine trysts that Jeff and Britta have pulled off and the cornucopia of costumes that Dean Pelton has managed to wear over the year. Meanwhile, Troy's pet monkey returns, only to disappear back into the school's ventilation system. On the case, Senor Chang quickly dives in to retrieve the monkey - along with all the loot he has stolen.

Source: NBC