First instance of the Dream-a-torium. This is Troy's and Abed's name for what is clearly a nod to the Holodeck on Star Trek: The Next Generation (1987). The room has a grid pattern same as the Holodeck when not generating any images.
The girl helping Jeff at the clothing shop called for "Doctor Tarpinian" in order to trick Britta during the phone call. Robert Tarpinian is the actor who plays the pizza delivery man seen in a few episodes, notably in Remedial Chaos Theory (2011).
When Pierce tells Annie that he can fix the outlet cover, he says, "Easy peasy, George and Weezie." The main characters of The Jeffersons (1975) were George and Louise Jefferson - George called Louise "Weezie".