And now the latest mystery, over a decade late: Is Monica a shapeshifter, or does the show just have bad editors?
A Friends fan noticed a scene where Monica isn't played by Courtney Cox, and the stand-in stands out with a really distinct profile.
Fans spotted a similarly awful stand-in from a Season 9 episode (it's season 9, you can tell by the girls' hair).
The Friends will be there for you. And if they can't, they'll send a stand-in.