I dreamed last night of a museum where all the exhibits were loving re-creations of different sitcom sets: Family Ties, The Jeffersons, Friends. The most interesting thing was that each of them was actually built with the "fourth wall" that home viewers could never see. In my dream, these ungainly trapezoids that look like no real living room you've ever seen actually worked architecturally with a fourth wall in place. [source]
Building the fourth wall of a sitcom set would be an interesting Photoshop or reality challenge.
Remember when The Manhattan Transfer appeared on Tool Time? WTF?