That's a great analysis of Miss Farrell's annoyingness, Julia—I think you're right that the show has failed to explain Don's interest in her and, as a result, has failed to engage the viewer's interest as well. As for her brother's Caesar reference, it could just be the latest evocation of the Decline and Fall theme. Or it could be more specific: a hint that someone is about to stab Don in the back. Of course, the cast of potential Brutuses is so large at this point, it's hard to say where that unkind cut might come from. Et tu, Sal? Et tu, Betty? Et tu, Bobby, who would like it if for once his dad would ask him how his day at school was?
A few stray items:
—Regarding Miss Farrell's little brother: Couldn't Don have driven another 20 miles and left the kid in Framingham? Maybe bought him a steak at Ken's? If Don's so concerned with the wellbeing of this afflicted young man, why not leave him at a gas station, at least, as opposed to the side of the road, with no sign of civilization in sight? Made for a nice visual—Don turning around the big Caddy on a ghostly Massachusetts road—but it didn't make much sense logistically.
—Roger Sterling Sr.'s widow stole the scene from her son. She seemed truly dotty, although I couldn't help wondering whether she was playing it up just a bit, so as to bust Roger's chops for taking up with such a young thing. Roger is forced to explain that Jane is his wife, not his daughter, prompting his mother to reply, hilariously, "Does Mona know?"
—I loved the brief glimpse into the old days at Sterling Cooper, specifically the story about Doug Thompson persuading Roger to eat a whole roll of laxatives on the pretense that they were candies. It seems that despite having the family name on the building, Roger got his share of hazing when he was coming up. Now that's a flashback I could have supported.
—We learned in this episode that when Roger discovered Don, he was working at a fur company and attending night school. So Don really does owe Roger a lot—we don't know exactly what he was doing for the fur company, or how big the operation was, but regardless, that must have been a pretty big break, being offered a job at Sterling Cooper. And the night-school detail makes sense. Don isn't like Connie Hilton—he doesn't play up his humble origins when mixing in society. It stands to reason that at some point he felt the need to acquire a bit of book learning if he was going to pass in the boardrooms of Madison Avenue.
—It turns out that even Lane doesn't like Moneypenny. "He's such a toad," remarks Lane's wife. "He is," Lane agrees. Almost makes you pity the poor chap.