This episode brought the return of Betty Francis, and provided an explanation for why we didn't glimpse January Jones in any "next week on" clips. The show's been holding onto the reveal that former model Betty has put on a few pounds, and is solving the problem of not fitting in her dresses by faking sick when it comes time to accompany her husband to events. A trip to the hospital for diet pills turns into a cancer scare when the doctor discovers a lump on her thyroid gland.
Betty's life has been defined by her being young and beautiful and something to be admired, but those are qualities that (weight gain or not) are fleeting. From her mother-in-law chiding that she's "give[n] up a little bit" to the doctor who didn't look her in the eye, the world is not treating Betty the same. And she's changing accordingly. Though she frets over tea with the friend getting serious treatment about how no one will hear one good word about her when she's gone, the dream she has later about her mourning family sitting at the table without her portends a shift toward actually thinking about the others in her life.
Paralleling Betty's fears about no longer being there is a workplace one about the dread of being replaced by someone newer and hungrier, of being made unnecessary. Roger's humiliation at the hands of someone he once hired has echoes in Peggy Olson's hiring of a socially awkward copywriter named Michael Ginsberg (and played by Ben Feldman), who, like her, is an outsider (he's Jewish) at Sterling Cooper Draper Pryce and is very talented. Peggy hires him despite Stan Rizzo's suggestion she pick someone mediocre who won't show her up, and insists she's not threatened by him, though the fact that he actually nails his interview with Don despite her concerns about it appears to irritate her more than the prospect of his failure.