When it comes to Friends, fans of the show have spent years scrutinising every small detail of every episode to find mistakes and little moments they'd never noticed before.
Many of these have gone viral, as fans spotted actresses seemingly changing places during scenes, stars being replaced by body doubles and filming equipment accidentally cropping up in shots.
And now it seems there's another little blunder that eagle-eyed fans have spotted, all to do with a guest star from season 8 of the show.
