Leonard: Buddy, I know me moving in with Penny feels like a big change, but it's not.
Sheldon: How can you say that? Amy's gone, and you two are married now, so it's only a matter of time before you're gone, too.
Penny: Okay, you don't know what's gonna happen.
Sheldon: No, I do. Eventually you'll want more space and you'll move into a house. And then instead of dinner a couple of times a week, it'll only be a couple of times a month. And then it'll only be on special occasions, like when Bernadette divorces Wolowitz.
Or-or-or like when Koothrappali's weird girlfriend admits where she buried his body.
Or Amy's wedding, where she's marrying someone better than me.