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The Absolute Worst Thing Amy Ever Did To Penny On The Big Bang Theory

If there's one character who stands out from the rest on The Big Bang Theory, it's undoubtedly Penny (Kaley Cuoco). Not only is she the only one of the series' core seven characters who isn't a total brain, but she's also the only one who doesn't have a canonical last name. While these seem like superficial differences, it may help explain why some of the characters on the show are particularly mean to her.

One character who has a history of treating Penny poorly is Amy Farrah Fowler (Mayim Bialik). Although the two ended the series as dear friends, their relationship wasn't always smooth sailing. After all, despite their future husbands being best friends, the two women initially had very little in common. Their distinctly different personalities led to an incident that is definitely the worst thing that Amy every did to Penny over the 12 seasons of The Big Bang Theory.

Amy gave Penny puzzles to compare her intelligence to that of lab chimps

The season 8 episode "The Comic Book Store Regeneration" is notable for featuring the death of Howard's (Simon Helberg) mother, Mrs. Wolowitz (Carol Ann Susi). It also has a rather nefarious side plot involving Sheldon getting jealous over the fact that Amy is helping Barry Kripke (John Ross Bowie) with his work. When he tries to wrap Penny up in his tantrum, she tells him to let it go. Sheldon wants a firsthand example of how someone lets something go, so he decides to get Penny involved.

He gets her mad by revealing that Amy has been giving her puzzles so she can test Penny's intelligence against that of some chimpanzees. At first, Penny insists that Amy hasn't been giving her puzzles, until she thinks back to the past few weeks and remembers that Amy has asked her to do strangely specific tasks, such as sorting a pile of coins by size and freeing a banana from a bamboo puzzle box.

Amy and Sheldon try to diffuse the situation by letting Penny know that she beat all of Amy's test chimps at the puzzles, with the exception of one named Barnabas, who was, "on Adderall." They also reveal that Sheldon has been giving Leonard the same tests. Although Penny remains upset about the tests, the situation is set aside after the group learns of Mrs. Wolowitz's death.

Amy and Penny move on from the betrayal, but it's not the last time that Penny will get mad at Amy for trying to test her.

That wasn't the only time Amy secretly tested Penny

In the season 11 episode "The Matrimonial Metric," Amy and Sheldon are planning their upcoming wedding. Of course, Amy and Sheldon being Amy and Sheldon, they can't just keep it simple. Instead of searching their hearts to decide who they want to have as their maid of honor and best man, the couple decides to conduct a series of tests to determine who out of their friends is scientifically the best fit for the job.

Although Amy isn't specifically targeting Penny with this round of tests, it still seems like a bold move considering how poorly Penny reacted the last time Still, it ends up working out in the end. The group finds out about Amy and Sheldon's tests and confronts the couple, who agree to call it off. The ordeal also causes Penny to realize how much she wants be chosen as Amy's maid of honor, which is a clear indication that Amy is Penny's best friend. When Penny reveals this information, Amy is overjoyed, and agrees that Penny should be her maid of honor.

Jealousy is another fault in Amy and Penny's relationship

The evolution of Amy and Penny's friendship hasn't just been marked by Amy cruelly testing Penny. On quite a few occasions, Amy has also found herself quite jealous of Penny. We can't say for sure if this jealousy is related to the bad behavior, but it certainly seems of a piece.

One of the earliest instances of jealousy comes in the season 4 episode "The 21-Second Excitation." While dining with the crew at the Cheesecake Factory, Amy overhears Bernadette (Melissa Rauch) talking about an upcoming girl's night she and Penny are having. Upset at not being asked, Amy eventually secures an invite to the girl's night, but she's not quite able to roll with the free-flowing grooming and dating talk. When asked to tell a dirty story, she recites "The Miller's Tale" by Chaucer in Middle English.

Bernadette and Penny's friendship proves to be another point of jealousy for Amy in the season 5 episode "The Isolation Permutation." While planning her wedding to Howard, Bernadette invites Penny to go dress shopping with her, and leaves Amy behind. When Bernadette finds out how upset Amy is over being excluded, she makes amends by asking Amy to be her maid of honor.

Of course, Amy and Penny are able to work through their relationship quirks and end the show as close friends, but The Big Bang Theory wouldn't have been nearly as entertaining if we didn't get to see all the bumps along the way.