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.
In a post on the How You Doin forum on Reddit, a viewer shared a look at a still from season four, episode 9, The One Where They're Going To Party.
The image shows a newsstand on the street filled with magazines and on the cover of one is Hollywood star Brad Pitt. Pitt is known by Friends fans for his appearance in the season 8 episode The One with the Rumour.
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