Penny and Leonard actually got engaged multiple times in before they finally decided to tie the knot. From the get-go, it was clear that the CBS nerd-centric sitcom was setting up the pair to be a couple. While the producers claim that they were open to them not ending up with each other, it was difficult to get any other love stories for them to progress because the public was immediately invested in their romance. This was the reason why Aarti Mann's Priya and Sara Gilbert's .

That being said, even when Penny and Leonard finally got together, things between them weren't exactly smooth sailing.

Throughout the early years of their dating, they encountered many issues — most of them were due to their circumstances and not because they had doubts about their commitment to each other. So despite many failed attempts to get engaged to be married, there was never uncertainty that one day, they would eventually tie the knot. Still, in retrospect, it was for the better that it took Penny and Leonard so long to be engaged because their initial reasons for wanting to get married were problematic.

5 The Launch Acceleration

While Leonard had always been in love with Penny, it took her a while to notice him. Even after they first started dating, there was a lot of apprehension in their relationship that they ended up separating. Inseason 5, episode 23, "The Launch Acceleration," however, Penny and Leonard have already dating for quite a while, that she started thinking about taking things to the next level, which resulted in them getting intimate. actually did this proposal quite creatively, as viewers were only shown the aftermath of it.

Apparently, in the heat of the moment, Leonard got carried away and proposed while they were in bed.

This surprised Penny, and not in a good way, causing her to storm out of the bedroom. Leonard profusely apologized and asked for a second chance, but Penny was quite irked about it, and understandably so, considering that they were working hard to take things slow in rebuilding their relationship.

4 The Tangible Attention Proof

In season 6, episode 16, "The Tangible Affection Proof," Leonard and Penny joined Howard and Bernadette for a double date during Valentine's Day dinner.

However, what was supposed to be a romantic night out, progressively turned bad after Penny noticed that her ex-boyfriend was proposing to his now-girlfriend. Visibly pissed, Leonard attempted to smooth things over by trying to get down on one knee himself, even though he didn't have a ring with him. Before he could even start with his speech, Penny sternly told him to get up.

This was arguably one of the worst moments for Penny and Leonard because it highlighted just how imbalanced their relationship was (at least at this point). Penny was getting fixated on her ex getting engaged without knowing that she was insulting her current boyfriend.

Seeing Leonard call her out on her behavior was satisfying, however. In the end, they eventually patched things up, with Penny admitting that she was self-sabotaging because of her commitment issues. This was also where they decided that Penny would need to be the one to propose.

3 The Hesitation Ramification

True to their pact, Leonard started becoming more careful about proposing, knowing that doing so freaked out her girlfriend. However, after Penny's career hit a major snag, she became convinced that the best way to fix her life was to get married.

So in season 7, episode 12, The Hesitation Ramification," Penny haphazardly proposed to Leonard while she was reeling about being cut from . It should have been the perfect opportunity to lock her into a life-long commitment, but Leonard knew better than to take advantage of her situation and said no.

Just because Leonard said no didn't mean that he didn't want Penny. However, it would have been a disaster if said yes to his drunken girlfriend's proposal. Perhaps Penny would have eventually taken it back once he sobered up. In any case, she eventually realized the error of her ways and Leonard's decision the next day.

Penny admitted that she was a mess and that motivated her unexpected desire to get married.

2 The Proton Transmogrification

Just a few episodes after Penny's botched proposal, the pair once again had an engagement conversation, oddly during Professor Proton's funeral in season 7, episode 22, "The Proton Transmogrification." At this point, both of them were already fairly comfortable in their relationship, to the point that they could even talk about deeper topics such as life and death.

Leonard opened up about his fears of having regrets before he passed away, and he cited turning down Penny's proposal as one of them. For her part, she pointed out that it was just the wrong time.

Professor Proton's death was one of the , but the pair's conversation about botched engagements brought levity to the outing. Ultimately, Penny proposed again, albeit in the most nonchalant way, after Leonard pointed out that she had turned him down twice, while he only had to decline her once. The whole scene was hilarious, but it had some significance to their relationship. It was further proof that they were at such a great stage in their romance because they could laugh about these things.

1 The Gorilla Dissolution

As it turned out, Penny and Leonard's fake proposal during Professor Proton's funeral was setting up their eventual engagement. Just after one episode in season 7, episode 23," The Gorilla Dissolution," the pair finally get engaged for real. The circumstance surrounding the engagement was familiar. Similar to when Penny's cameo was cut from NCIS, she was distraught over how her career was shaping up when she suddenly brought up the idea of getting engaged.

The difference this time was that Penny was able to properly justify why she wanted to marry Leonard in episode. She explained that she didn't really need external validation, she only needed her boyfriend. This warmed Leonard's heart and ultimately convinced him to take the idea seriously. What Penny didn't know was that Leonard had been secretly carrying a ring in his wallet, indicating that he had long been set on marrying her.