Jennifer Aniston was REPLACED as Rachel in Friends in decade-long secret\rbrOne eagle-eyed fan spotted the gaffe in season nine and thankfully just couldnt keep it to themselves\rbrA decade-long Friends secret has been exposed - and its a juicy one.\rbr\rbrIt turns out Jennifer Aniston , who played Rachel Green, was replaced by another actress during season nine.\rbr\rbrIn the series 209th episode - titled The One With The Mugging - it appears that a stand-in played the part of Rachel in one scene.\rbr\rbrEven though most fans have seen every episode time and time again, the secret has gone unnoticed for more than a decade.\rbrThat was until super fan Jordan D’Amico spotted the error during a routine binge and posted it online.\rbr\rbrTaking to RecentlyHeard, he wrote: Only a few minutes into the episode, an enthusiastic Rachel rushes into Monica’s apartment to tell Joey that he got an audition with the famous and fictional actor, Leonard Hayes, played by Jeff Goldblum.\rbrThe three friends admit to admiring the actor for his cell phone commercials in which he starred opposite a monkey.\rbrMonica zealously posits that perhaps the monkey will be at the audition. Joey reacts by saying, Don’t make me more nervous than I already am! and goes to sit back down.\rbr\rbrIt’s at this point that… BAM!\rbr\rbrRachel is even wearing different clothes - how did we not notice?\rbrUnexpectedly, the spotting has since started to spread around the web with others coming forward to confess theyd clocked similar gaffes.\rbr\rbrOne Twitter user posted a screenshot claiming that theyd noticed Courteney Cox being replaced in one episode too.\rbr\rbrWe have contacted NBC for a comment on the mystery.