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

Leonard and Penny's relationship was destined from the very first episode of The Big Bang Theory in September 2007. The pair met just minutes into the pilot of the hit sitcom, and Leonard (Johnny Galecki) was instantly lovestruck by the bubbly blonde waitress moving into the apartment across the hall. It took the shy experimental physicist some time to work up the courage to actually ask Penny (the always-hilarious Kaley Cuoco) out after plenty of will-they-won't-they tension, even failing to clarify on the first attempt that it was a date. When the couple eventually did start dating, they were on and off for a few seasons of The Big Bang Theory, but most people were rooting for the pair to end up together despite their many differences.

That said, no relationship is perfect, and Big Bang Theory fans had to watch plenty of ups and downs in the Lenny (that's Leonard plus Penny) relationship. During their partnership, Leonard did many wonderfully romantic things for Penny (how many of us can say someone brought us a snowflake from the North Pole?), but he also did plenty of horrible things to her along the way as well.

It's difficult to pinpoint just one awful thing Leonard did to Penny, considering he has a miles-long list of interpersonal crimes on his record. There was his insane jealousy when Penny had an old boyfriend sleep on her couch just weeks after they started dating (the first time), plus another ugly jealous streak when Penny was doing a college assignment with a classmate. There was also the time Leonard refused to support Penny's dream to become an actress, then subsequently became envious when she found success in a new career and started making more money than him. Additionally, Leonard rewrote Penny's college paper because he didn't think hers was good enough, read her diary, didn't tell his mother he and Penny were dating, and hid money from Penny because he didn't trust her to know how to spend it. 

Compile some of Leonard's worst deeds, and it reads almost like a list of red flags women are advised to avoid on the dating scene. But what's the worst thing he ever did to Penny? There are many to choose from throughout their relationship, but as far as we're concerned, ruining her wedding day takes the cake (no pun intended). 

After a lengthy engagement and still no sign of any wedding planning, Leonard and Penny decide on the season 8 finale of The Big Bang Theory to take a spontaneous road trip to Las Vegas and tie the knot there instead of putting on a big white wedding. Probably not the happily ever after fans were hoping for when it came to Lenny, but the last-minute decision kept in line with Penny's more relaxed personality. 

As laidback as Penny usually is, everyone knows that you don't mess with the bride on her wedding day. It's decidedly uncool on an occasion when most women are already stressed and excited at the same time. Adding another emotion to the mix is just asking for bridezilla to make an appearance. However, in the car on the way to Vegas, Leonard decides it's the opportune moment to tell his fianceé on their wedding day that he actually cheated on her a few years back. Of course, Leonard — what a woman really wants to hear as she's about to walk down the aisle is that her betrothed lip-locked with another woman while they were together. What's worse is that this confession came after Leonard had been incredibly jealous every time Penny had anything to do with another man throughout their relationship — and, honestly, even when they weren't a couple. 

Naturally, Penny wants to know why Leonard would choose that moment to tell her, so he throws back in her face that she was the one who said they know everything about each other. It's clearly a defense mechanism for realizing he made a mistake confessing his moment of unfaithfulness, but still one that tries to make her feel like she's at fault for him blurting it out. When Leonard asks what he's supposed to do about it, Penny responds, "Keep your mouth off other women?" — which, frankly, seems like a fair request within the confines of a relationship. 

Ultimately, Penny decides to go through with the wedding, but the effects of Leonard's confession show almost instantly. After being giddy when they first set off to Vegas from Pasadena, Penny suddenly seems annoyed with the details of the day, even responding with "don't push it" when Leonard said their wedding day would be the happiest day of their lives.

The Big Bang Theory season 8 finale ends on a cliffhanger, the narrative picking up again with the season 9 premiere. On that episode, Penny still appears to be irritated by Leonard's attempts to organize their wedding details once they arrive at the wedding chapel. When they head back to their hotel room to start their honeymoon after saying their "I do"s, Penny can't even kiss her new husband without picturing him doing the same with the other woman. Penny experiences yet another unpleasant revelation when Leonard tries to calm her down: he lets it slip that he actually works with the woman he cheated on Penny with, and regularly sees her at the university. Leonard's solution to Penny's latest wave of anger is suggesting that they try to make a baby, which is the least appropriate response to the situation at hand.

By the time they arrive back home, Leonard is yelling at his new wife and trying to lay some blame at her feet. Penny is so angry about the whole situation that she heads straight back to her own apartment and slams the door in Leonard's face, and thus the pair spend their first night as a married couple apart from one another. It's only at the end of the season 9 premiere that Leonard finally acknowledges — mind you, to his roommate Sheldon (Jim Parsons), and not his new wife — that he's definitely the one at fault for this argument. 

The advice to not mess with a bride on her wedding day is certainly well-founded, but it seems as though the couple's marriage was over before it even began as a result of Leonard's confession. Thankfully for Leonard and Penny, they are able to stick it out and open up with one another about their insecurities and fears within their relationship. And by the end of The Big Bang Theory, Penny is pregnant (albeit accidentally) with Leonard's child. All's well that ends well?