We've been binge watching episodes of Friends since they were made so available on the likes of E4 to more recently Comedy Central before they were added to the streaming giant that is Netflix.
If we had to guess, we'd say that we have re-watched all ten series of the six-some at least 16 times.
And as perfect as we think Friends is, and it's pretty perfect, like every show it's had its few mistakes but this one has been hard to find and has only been picked up lately.
It takes place during series 2, episode 21 titled: 'The One With The Bullies' also known as the episode where Phoebe goes to the home address of her 'real father'.
However, as Joey, Rachel and her pull up to the gate in her old yellow taxi, there's a vicious dog outside who keeps jumping up the side of it.
However, when the camera angle switches to inside the cap, it's clear to see that the top of the dog-handler's head is visible through the car window.
The episode is called 'the one with the bullies' because it is based around Chandler and Ross' coffee house fued with two other guys who take their seats.
See can you spot the mistake in the Friends episode in real time here.