Stan has essentially been Peggy's work husband for several of Mad Men's last seasons, but the series finale confirms that they're also soul mates. They get into a little tiff in the office, but later on the phone, Stan ends up confessing that he's in love with her. Peggy needs about a minute to think about it, but soon she comes to her own conclusion that she's also in love with Stan. In case you're thinking this comes out of left field, take a look at Peggy and Stan's relationship throughout the years. While Don's fate has been up in the air (and eventually ends as cryptically as you might think), these two lovebirds have been meant for each other since the early days.
He claims it's to calm her nerves, but it's totally not.
Even if you hadn't been paying attention to their budding romance, it's still wonderfully satisfying.