If you're one of the thousands of 'Friends' superfans who can recite multiple episodes by heart, then you know that the show isn't the paradigm of perfection some will have you believe.
You've probably watched each episode dozens of times and keep coming back for more.
And like any repeat binger, you've probably picked up on little quirks you didn't catch the first several times you've watched an episode.
'Friends' is by no means a perfect show — there are little mistakes in most episodes, nearly imperceptible to an untrained (and inexperienced) eye.
One fan took to TikTok to point out a flaw she found in season eight's episode five, 'The One With Rachel's Date,' in which Monica is replaced by a random woman.
In it, Phoebe and Monica are in the middle of a heart-to-heart on the couch of the iconic 'Central Perk' coffee shop.
They're discussing Monica's sous-chef, Tim, with whom Phoebe has been having a fling.
Monica is thinking about firing Tim, but Phoebe is trying to convince her to give him another chance.
As the camera pans over to Monica for her reaction, the woman sitting on the couch was not, in fact, Courteney Cox, the actress who played the famous character.
Instead, it's some other woman who was filling in for Cox.
"I know there is so many mistakes in friends but I have never seen this one before," @mumandmore4 captioned her TikTok.
The TikToker found the blunder while watching 'Friends' on Netflix, which uses a wider screen than those the show aired on when it came out in 1994.
Several users reacted to @mumandmore4's findings.
"You are soooooo far behind, we knew this years ago," wrote @kez_1403.
"Why would they substitute Monica tho? like, she was there for a bit of the scene, then left?! lol," asked user @beejaygee.
"Sometimes when they need to get one actor on camera, it's too expensive to hire both actors," answered @barlondo. "So they hire readers / stand in actors."
Each member of the full cast was paid an estimated $1 million per episode.
'Friends' is no longer on the U.S. version of Netflix — the show was taken off the platform in January 2020.
But American fanatics can still watch the sitcom with an HBO Max subscription.
And as they do, they're sure to find more mistakes, just like the one @mumandmore4 discovered.
* Follow Mirror Celebs on Snapchat, Instagram, Twitter and Facebook.
