Penny went from being Leonard and Sheldon's new neighbor to a best friend in a matter of weeks. There's something very open and trusting about Penny that is totally different from Leonard, Sheldon, Raj, and Howard. She had selfish tendencies with the guys at first (using their WiFi, stealing their food...) but they eventually became a small, understanding family.

As sweet and helpful as Penny was to the guys, they didn't always treat her in the nicest of ways. And although Leonard is her husband, there were plenty of times he treated her poorly as well.

When Howard Was Far Too Forward

How did a big transformation from season one to the final season but fans still remember how he used to be. When Penny moved in and became quick friends with everyone, Howard tried everything to get Penny to like him. It got to the point where Penny couldn't take it anymore. All of his gestures and compliments became creepy so Penny told him off. The gang thought Penny was too hard on Howard (even though he was the one treating her like a piece of meat), so when she stopped over to apologize to him he tried to kiss her!

Raj Made Her Think They Slept Together

Penny always had a soft spot for Raj but there were times where he surprised her with his vulgarity. As friendly as the two were, they crossed a line in their friendship when they had too much to drink and spent the night together.

For days Penny was tormented with the thought of her sleeping with her ex's best friend but unbeknownst to her, they never slept together. However, Raj wanted everyone to continue thinking they did. He knew how torn up over it Penny was but used their night together as bragging points regardless of her feelings.

Leonard Cheated On Her

Through all the ups and downs, these two always found a way back to each other but it wasn't without its hardships.

On the way to Las Vegas to get married, Leonard dropped the bomb that he cheated on her with a woman while he was at sea. He assured her they only kissed but it was enough of a bomb to throw their marriage through the loop. Leonard was the one guy Penny could always count on, and knowing he cheated on her was a betrayal of her trust.

Sheldon Broke Into Her Apartment And Cleaned It

When Penny became more comfortable with Sheldon and Leonard, they let each other into their apartments more frequently. What Penny didn't think, however, is that one of them would enter her apartment while she was sleeping...

In the middle of the night, Sheldon couldn't sleep knowing an apartment as messy as Penny's was just across the hall. He let himself in and organized her whole apartment for her. While that sounds nice to some people, Penny found it extremely weird and that Sheldon had no boundaries. The two eventually got over it and became one of the best friend pairings in the show.

Howard Found A Revealing Blog Written About Penny

she didn't deserve to be shamed for her promiscuous ways. Before she settled down with Leonard, Penny went on plenty of dates and was seen with a different man leaving her apartment time and time again. But after she found her date's blog online that detailed their intimate relationship, she was horrified. She felt embarrassed and cried on Leonard's shoulder over her private life becoming public. Instead of protecting Penny, Howard and Raj were all too happy to scour the Internet for it and read it happily while she cried in her apartment.

And When Howard Slept With Her Friend

then the next best thing was for Howard to date Penny's friend.

When Penny's fake-friend Christy came to visit Penny from Nebraska, Howard took advantage of the trip once he heard she was easy. The two spend the entire weekend in Penny's apartment (much to Penny's chagrin). He even invited Christy over to his mom's house! Penny hated the fact that Christy was staying with her but hated Howard bathing in her tub more.

Raj Took Credit For Her Work

In "The Comet Polarization," the gang is on the rooftop using a telescope to watch Mercury but when Penny sees something fuzzy in the sky, Raj takes a picture of it to prove that she saw nothing. But as it turns out, Penny saw a comet. Instead of giving Penny credit for finding the comet, he took all the credit and sent "his" findings into work. Penny was devastated because that was the one cool thing she's ever done in the science world and it was rude for Raj to dismiss her. I but it's another to treat her like she's dumb and that her work doesn't matter.

Leonard Never Told His Mom About Penny

To be fair to Leonard, his relationship with Penny was too unstable for him to run home and tell mommy about it. Especially given the fact that Beverly didn't entirely care too much about Leonard's personal life anyway. But when Beverly was coming into town, . Leonard explained that his mother was cold and compared everyone to Leonard's siblings. Penny felt embarrassed that Leonard was ashamed of her and her job as a waitress so she took it in her own hands to win her over.

Sheldon Didn't Care About Her Pregnancy

The relationship between They had a brother and sister vibe about them that no one else could understand. And as close as they were by the final season, Penny and Leonard were surprised when Sheldon made their pregnancy about them.

While on the flight, Sheldon saw Penny vomiting uncontrollably and thought she had the flu. When Leonard told her she was pregnant, he didn't care at all; he was just happy that he wasn't going to catch what she had. His dismissal of their future baby was upsetting to both of them.

Sheldon & Amy's Secret Experiment

In "The Comic Book Store Regeneration," Penny found out that Sheldon and Amy were running secret experiments on her to see if she was smarter than a chimpanzee. From opening a banana to opening tricky boxes, Penny did what she could without realizing that the couple were taking notes on her results. Amy, of course, didn't realize how insulting this was at the time but it only made Penny feel used and dumb.