The first time we meet Oliver's ex-girlfriend Tamsin, he asks her if her breasts are bigger, and she tells him that no, they're just more inaccessible to him. But in later episodes, we learn that she is several months pregnant, meaning that yes, her breasts really were bigger, and Oliver is more perceptive than he at first appears.
During the episode "Inferno," after Jane's very vague grasp of what vegetarianism is, we get this exchange between her and her therapist at dinner:
Jill: A vegetarian is someone who does not eat meat, you insane bitch. Jane: I get enough of that language during our sessions.
Realize that Jane is so screwed up, she has sent a licensed health professional so over the edge, she's insulted her repeatedly — even calling her "insane", which is not a word psychiatrists are generally fond of using. It was our first major glimpse into how messed up Jane really is.
Jill: We agreed two months ago to end your therapy, it was going nowhere.
Jane: I thought that was just an exercise to help me cope with rejection!
Jill: No, that was rejection.
In the fourth series, Jill re-appears as the woman running Susan's ante-natal class; the inference is that Jane caused her to give up being a psychiatrist, and she retrained as a pregnancy specialist in order to avoid Jane (who she probably reasoned was so crazy that most men wouldn't want to sleep with her, and that the chances of her getting pregnant were therefore rather slim). She's obviously very upset when Jane shows up at the class pretending to be pregnant.
