We know. There are many questions. What? How dare they? When? WHY?
But most importantly, how did we not notice?!
Thankfully the eagle-eyed Jordan D'Amico spotted the unthinkable for us, during a routine binge watch.
In The One With the Mugging episode in the opening scene, Rachel, for reasons we can only be offended by, was replaced by another actress - looks as though we were the ones mugged off!
Initially, Jennifer Aniston is stood in the kitchen with both Monica and Joey, talking about Joey's new audition, but when the shot cuts back to Rachel and Joey standing there together, 'Rachel' is actually a different person.
Blasphemous though it may be, it also happened to Monica during a conversation with Phoebe in Central Perk.
What is life?