"Friends" has some of the most loyal fans in the world - fans who could recite pretty much any line from any episode at any given moment - but it took one dedicated and very detail-oriented fan to spot the two episodes with doubles for Jennifer Aniston and Courtney Cox that have somehow gone unnoticed all of these years.

Now that the iconic sitcom has been over for nearly a decade and is on Netflix being binge-watched, more and more small details about the show are being discovered. Jordan D'Amico, a writer for Recently Heard, noticed two episodes where Rachel (Aniston) and Monica (Cox) had doubles for a split second.

The first stand-in takes place in season nine during the 15th episode, "The One with the Mugging." Just a few minutes into the episode, Rachel runs into Monica's apartment to let Joey know that he got an audition and as Monica begins to explain some things to Joey, you can see a girl, wearing the same outfit, that is most definitely not Aniston standing on the left hand side of the screen. "Who the hell are you and what did you do with our beloved Rachel?" D'Amico wrote.

The second stand-in took place during season eight, only this time it was for Cox's character in "The One With Rachel's Date," according to People. Monica and Phoebe (Lisa Kudrow) are sitting in the famous Central Perk coffee house when the camera cuts to Phoebe and you see a double for Cox sitting on the couch beside her. It's incredible that it took this long for people to notice, but it makes you wonder how much more you may have missed over the years from your favorite shows.