The Big Bang Theory: 21 Easter Eggs You Probably Missed

7. Apartment Flag Is Upside Down

Another example of a recurring 'prop' is the inclusion of the apartment flag on Leonard and Sheldon's fridge. Sheldon explains that the flag must be turned upside down if the apartment is in distress.

Throughout the series it is seen to reflect events, with the flag upside down during conflict, and the right way during relaxed times. It's just another little bit of fun the producers want to have with the audience.