Since Friends launched on Netflix at the start of this year, eagle-eyed viewers in the US have been picking up on a few mistakes that went unnoticed until now.

Some of them, like the 'Reserved' sign at the Central Perk, have cleared up things we've long wondered about – how DID the gang always get the same table without having to fight off other coffee lovers?

But other "mistakes," like this one discovered by entertainment site Recently Heard, have totally weirded us out.

Season 9, Episode 15 (The One With The Mugging) might seem perfectly normal, until you spot one GLARING error. Here's Joey and Rachel, standing casually in Monica's apartment:

The camera cuts away to Monica, then it goes back to Joey and Ra- OH WAIT:

Before you go writing to NBC to complain though, there is a very rational explanation for this impostor. Back in the days of the show's original release, when the series were only available to buy on VHS, most TVs used a 4:3 aspect ratio.

With the dawn of widescreen, we now view our shows from a wider angle, meaning we get to see a few extra centimetres on either side of the screen that would previously have been hidden. 

The result? All those stand-ins that were used when Jennifer, Courteney and the gang were busy getting their make-up done or chilling in their trailers are now VERY clearly visible.

Here's another example, this time of a Monica who is most definitely NOT Monica.

We're questioning everything we thought was real life.