11 Things You Totally Missed In Friends
3. Moving Apartments
Monica's apartment is well known now as being number 20, however it was actually quite different when it first started. Back at the beginning of the series it was shown that she actually lived in apartment 5, but the producers changed it when they realised their error of 5 not being high enough in the building. Subsequently, Joey and Chandler's apartment was also changed, from number 4 to number 19.
However, that wasn't the last of the notable changes (or lack of them) for the apartment numbers). In a flashback scene that takes place before the series starts, it shows Monica's door once again, only it still has the number 20 on it, when really it should be number 5. Similarly, Ross moves into apartment 3B, but this disappears off the door in subsequent episodes.
Another point of note with the apartments is that they discuss at the end of the show how all the characters have lived in Monica's, however what's not mentioned is the fact that they've actually all lived in Joey's as well.