1. Something Mary would never admit to anyone, even under pain of death, was that the ratio of "times she was actually annoyed with Marshall's trivia" to "times she said she was annoyed" is embarrassingly low. At some point, it switched from being annoying when they first started working together, to being background noise, to being kind of cute. Over the years, it had become a sort of soothing background noise by its constant presence, and when he wasn't around, she kind of missed it. Not that she'd ever give him the satisfaction of telling him that.
2. If Marshall really wanted a fancy wedding, if it was really important to him, she would have done it. She wouldn't've put it past him to have the entire thing planned out in the kind of girly fantasy she never understood. She would have felt ridiculous the entire time, but she'd do it for him. Still, when they did end up down at the courthouse, she was incredibly relieved.
3. Mary didn't like feeling trapped. Anyone who knew her for more than five minutes could figure that out. Marshall managed to hit the perfect blend of "I'm not trying to hold on to you and if you want to leave I wouldn't turn it into a big deal" and "but I do care about you a lot." She was surprised that he asked her to marry him, but she wasn't surprised that he managed to do it in the most non-threatening way possible. That was probably the only way she would have ever agreed to marry him, considering what happened with her last two attempts at marriage. It was hard to feel like she needed to get away when faced with a piece of candy as an engagement ring, and the guy asking her was telling her that if she said no, it wouldn't matter.
1. Marshall had a Twitter account. Originally, he signed up because having all of @MythBusters's tweets forwarded to his phone was the easiest way to get notified when they were looking for volunteers. (One day, he was going to take a vacation and be able to make it up to California to be a volunteer.) But it didn't take long before he started following Adam and Grant, too. After that, it was just a slow slide into following more and more people. He tried to keep Mary from seeing his screen when he was reading tweets, knowing there would be no end to the mocking if she ever found out. (He was right.)
2. Marshall never actually planned to ask Mary to marry him. In fact, his plan for the future with Mary didn't contain anything that even resembled getting married, because the idea of Mary agreeing to marry anyone again was ridiculous. He didn't need that as proof that she loved him. But one of the kids of one of his witnesses had given him the ring pop earlier that day, and when he reached into his pocket, planning to eat it, it just felt like a moment. Later, if he was going to get all mushy about it, he'd call it serendipity (but he'd never say that to Mary's face).
3. Still, the instant the words left his mouth, he realized that what had sounded like a good idea in his head for the five seconds he thought about it was actually a horrible idea. It wasn't that he didn't want to marry her; he fully intended to spend the rest of his life together, as long as she didn't have other plans. But if there was one thing that would make Mary head for the hills, he was pretty sure it would be a proposal. He spent the next couple seconds trying to act as calm and nonchalant as possible while he frantically tried to figure out damage control. When she said yes, he couldn't have been more surprised than if she'd sprouted wings and a tail. After years of being her friend, and years of dating, he had become very good at covering shock with teasing. It turned out that was also useful for covering incredible relief.