Fans Noticed That 'Friends' Used A Fake Jennifer Aniston

In the episode titled "The One With the Mugging," "Friends" producers used a Rachel Green stand-in, but no one noticed.

As you can see here, while only a portion of the woman's face is visible, she is indeed NOT Rachel Green, or if you wanna get technical, Jennifer Aniston. What in the world is happening.

And by the way, if you look closely at this and the previous photo, the two "Rachels" are not even wearing the same type of shirt. Wow, using stand-ins really doesn't seem like a difficult gig.

There is an explanation why no one realized this. Trust us. One Twitter user noted that viewers didn't see this because it originally aired in a different format. As HD switched from a 4:3 ratio to 16:9, the "Friends" stand-ins have now become visible. Everything we know is wrong.

And oh, it gets better. There's even a fake Monica. Regular Monica is seen above, about six minutes in to "The One With Rachel's Date" from Season 8, episode 5, according to Huffington Post.

Look to the right. WHERE IS MONICA AND WHAT HAVE YOU DONE WITH HER.

Here's what we say to this shocking development.

There are a number of TV shows that actually tried to replace their iconic characters over the years, not just use a stand-in for a quick break.

The most recent is likely the two Beckys that appeared on Roseanne. The reason had nothing to do with the quality of performance for Lecy Goranson or Sarah Chalke, but more to do with Goranson's educational pursuits.

It became a running gag on the show, even with its revival.

When Dick York had to leave Bewitched due to back issues, he was replaced as Darrin -- the loving husband to Samantha -- by Dick Sargent. This did not go over well with audiences and the show soon fell out of favor.

Catwoman on the original Batman television series was played by three different actresses over the course of the show's run and its film release.

Julie Newmar famously played the most iconic of the Catwomen on the show, followed by Eartha Kitt in a memorable performance. But when the film version came around, Newmar didn't even know and Lee Merriweather was given the role.

Adam West always played Batman, though.

Beverly Owen was replaced on the original Munsters show by Pat Priest after only 14 episodes. Many didn't seem to notice, possibly because of the outrageous looks for the rest of the family or possibly because both women looked like carbon copies of each other.

The original Laurie Forman, Lisa Robin Kelly, is actually a sad story. She was forced out of the show due to problems with substance abuse according to Variety, replaced later with actress Christina Moore.

It was a strange change after five seasons, but one that highlighted a sad truth about Kelly's career and life. She would die from an overdose in 2013.

Fans of the long-running show MAS*H were faced with a big change when Henry Blake, played by McLean Stevenson, was killed when his plane was shot down. Of course, Col. Sherman Potter stepped in and was the voice of reason for the 4077.

When actor Nicholas Colasanto died in 1985, "Cheers" fans were devastated. Woody Harrelson, who played the clueless Woody Boyd, came in and provided much needed levity. Woody went on to become a calm, reassuring character in the NBC comedy.

The NBC show "Newsradio" was shocked when actor Phil Hartman was murdered by his wife in 1998. Hartman, an SNL alumnae, played the arrogant Bill McNeal on the successful news comedy, and became one of the show's best-loved characters. Jon Lovitz then stepped in as Max Lewis, and things kind of tanked from there.