3. Play It Again, Brian
The long running arc of Brian's unrequited love for Lois is central to the episode Play It Again, Brian in which he invites Peter and Lois to hear him read an extract from his award-winning essay at Martha's Vineyard. The couple agree as they have been suffering some marital difficulties and recognise the need to get away together, but Lois' displeasure with Peter is only exacerbated on the trip, which leads to a situation where Brian attempts to kiss her. This causes major conflict between Peter and Brian, with the dog accusing his owner of treating Lois like garbage. Although he has Lois' best interests at heart, she decides to remain with Peter, despite admitting to sharing his feelings for her occasionally. This confusing romantic triangle provided a lot of humour and got the sexual tension between Lois and Brian aired out suitably,and more importantly the episode also subsequently relegated the romantic feelings to mere references and allowed Brian to pursue other meaningful relationships. Brian's credentials as a romantic are spotty, he even admits to having plagiarized most of his article, but it comes from a good place. He's unlucky in love but it's not for lack of trying, and while we rooted for Brian, sadly he never found his soul mate.