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

Oil and water, Lea Michelle and her co-stars, and Sheldon and Penny — some things just don't mesh. The across-the-hall neighbors spend a fair amount of The Big Bang Theory's 12 seasons bickering and feuding, and although they eventually become friends, it's clear that there is something other than a genuine fondness for one another at the center of their relationship.

Although Penny (Kaley Cuoco) takes pleasure in picking at Sheldon's (Jim Parsons) prickly personality quirks, it's often the theoretical physicist who is the instigator of their fights. In fact, throughout the run of the show, we've seen Sheldon be downright cruel to Penny on a number of occasions. He's usually a bit mean to the people in his life, but it feels like he saved some of his worst behavior especially for Penny.

If we were to list all the insults and degrading comments that Sheldon lobbed at Penny over the years, this article would rival War and Peace in length. So, instead, we're going to focus on the absolute worst things Sheldon has ever done to Penny on The Big Bang Theory.

Sheldon tries to train Penny by giving her chocolates

At the heart of Sheldon's dislike of Penny is the fact that ... well, he simply does not like her. In the season 3 episode "The Gothowitz Deviation," Sheldon has to contend with the fact that, now that Penny is dating his roommate, Leonard (Johnny Galecki), she's going to be around the apartment much more frequently. Instead of getting over it and learning to get along with her, he comes up with a different, and much more, malicious plan.

When Leonard notices that Sheldon keeps giving Penny chocolates, he confronts his roommate about his unusually friendly behavior. It's then that Sheldon reveals what he's up to: He's attempting to train her to stop doing things that annoy him using positive reinforcement. Of course, Sheldon being Sheldon, he has a scientific explanation, saying, "I decided to employ operant conditioning techniques, building on the work of Thorndike and B.F. Skinner. By this time next week, I believe I can have her jumping out of a pool, balancing a beach ball on her nose."

Trying to train an adult person like a circus seal is a pretty despicable thing to do. While we're on the topic, Leonard probably should have made Sheldon cut it out, or at least told Penny what was going on. On the other hand, the fact that Sheldon is figuring out ways to deal with Penny being around the apartment at all is a step forward in their relationship. After all, at one point, he banned Penny from coming into the apartment altogether.

Sheldon once banned Penny from entering his apartment

Things got extra-hostile between Sheldon and Penny in the season 2 episode "The Panty Piñata Polarization." Penny comes over to Sheldon and Leonard's apartment to watch TV, and when she tries to sneak an onion ring off of Sheldon's plate, he announces that she now has two strikes against her (the first was for sending Sheldon an "I can has cheezeburger?" meme). Outraged at Sheldon's policing, Penny sits in Sheldon's spot and refuses to leave. This earns her third strike, and Sheldon banishes her from the apartment.

This sets off a war. Although Penny gets in a few good shots of her own, it's Sheldon that takes the most drastic action. While she bans him from eating at The Cheesecake Factory, Sheldon takes all of Penny's clothing and hanging it up on the electrical wiring outside of the apartment building. Penny gets Sheldon back in the end by ratting out his bad behavior to his mother, but he was clearly the more aggressive party in their battle.

What makes Sheldon's mistreatment of Penny even worse is that he belittles her out of one side of his mouth, and asks her for favors out of the other.

Even though he torments her, Sheldon still expects Penny to do him favors

You would forgive Penny if she didn't want anything to do with Sheldon after some of the ordeals through which he's put her. For some reason, however, she works to maintain their frienemyship throughout the show. This strange dynamic is on full display in the season 2 episode "The Euclid Alternative."

One of Sheldon's most endearing (or obnoxious, depending on how you look at it) qualities is that he doesn't know how to drive. This is especially difficult, considering he lives in Los Angeles and needs a car to commute to work. He traditionally relies on Leonard to carpool to Caltech, but when Leonard begins working nights, he needs a new patsy to drive him around. For some reason, he goes to frequent punching bag Penny for the favor, and for some reason, she agrees to do it.

To Penny's credit, she puts an end to her chauffeuring duties before she even makes it to the university. After enduring a few minutes of Sheldon's criticisms of her driving and his badgering about her "Check Engine" light being on, Penny ends the ride early by letting her tormenter off on the side of the road.

Considering the two are still friends by the end of the series, it's clear that Penny has either forgiven or forgotten the terrible things Sheldon did to her in the past.