No, this isnt a Welsh character who found his way to Madison Avenue in the 1960s, but the name of the college attended by Dons first wife, Betty. Back in season one episode The Ladies Room, she says that her neighbours jealousy reminds her of her days in a sorority at Bryn Mawr. While its easy to imagine Betty as being part of a sorority, there was just one little problem with this; Bryn Mawr didnt have sororities. Matthew Weiner commented on this error, telling the New York Times: Maggie Siff, who played Rachel Menken, went to Bryn Mawr, and she said thats wrong. You do what you can.