We've watched Friends so many times we know it word for word. We get the most obscure inside jokes. We've even daydreamed about swapping our real life mates for Ross, Rachel and co.
But, however well you know Friends, chances are you didn't notice this: the fact that Monica and Joey's apartments just inexpicably change number.
Monica starts off living in flat 5, while Joey and Chandler reside in number 4. Nothing new there, eh?
But by episode 10 of the first season, Monica and Rachel are living in apartment 20, with Chandler and Joey having swapped to 19.
Could we BE any more confused?
With no reference to the apparent move, we can only assume showrunners decided to make a sneaky switch to make the fact that the gang lived on the sixth floor more realistic.
But whatever the reasoning our minds are officially blown.