One of the messages that Megan tells Don he got after his anti-tobacco ad is from an "Emerson Foote." Foote was chairman of the powerful advertising firm McCann-Erickson in the mid-1960s when he resigned and publicly spoke out against the tobacco industry, which was a large part of McCann's business. He later became an anti-smoking activist and the chairman of the National Interagency Council on Smoking and Health.
Midge tells Don, "I'm glad you haven't changed." This refers to the fact that Don gave her money, like before, but also, throughout the series to this point, and the entire series eventually, he always looks (dresses) the same no matter how styles change around him.