While we’re growing up, most of us will reach a clashing conclusion – whether witnessing an over-affable uncle at a wedding, or a feckless father weeping at a wake, we’ll cruelly say to ourselves: “I don’t want to be like that.” Whether we say it loudly or bury it beneath, there are some traits within our bloodline that one wishes to be withdrawn from the family circle. But family is family, and while you cannot escape some harsh inevitabilities, you must also learn to love what you have – Lisa the Simpson is a lesson in both.

Smart, solitary and in possession of a strong social conscience. Those three accurate assumptions of Lisa Simpson’s character are jarringly juxtaposed with those of her family members, particularly the men. It’s something that has come up frequently throughout the series – from Lisa’s brief, but brutish, barbs at the ape-esque Homer in Lisa’s Substitute, right through to the feeling of disassociation in Summer of 4 ft 2 – but has never been tackled as full-on as it is here. In this episode, Lisa finds herself “descending into mediocrity”, and fears that she will inherit the idleness of her couch-dwelling father. It’s sweet but strong, provoking questions of whether Homer was, too, a talented youngster who plunged into passivity.

That query is answered, devastatingly but unreliably, by Grandpa, who informs Lisa of the “Simpson gene”, an absurd but agreeable assumption that, as adolescence ascends, intelligence is replaced with humdrum grades, listless attitudes and boorish pastimes. It’s an ironically dumb plot device, but as it comes from the vegetative vowels of Abe, we’re left satisfactorily unsure of its credence.

This then leads to the rest of the episode. Being Season Nine, it alas falls somewhat flat – where Summer of 4 ft 2, an episode devoted to Lisa’s emotional turbulence as an outsider, was sweet and funny, Lisa the Simpson feels a little rushed and unsure. But, luckily, any episode featuring Lisa is naturally going to exude pathos, a bittersweet premise and a heartfelt ending.

Another idea that the episode portrays is the importance of family. Similarly to the great Lisa’s Wedding, Lisa may have contrasting interests than those of her family (sans Marge, perhaps), but she still loves and cares for them, as well as possessing enough similar traits to keep the theory of adoption at bay. Here, instead of wallowing in her news, the stoic brain in Lisa ironically compels her to experience the life of an underachiever, which involves watching hilariously kitschy reality shows with Homer and Bart. It’s sweet and funny how Lisa tries hard to harbour a zest for such trash, and I particularly like how she grouses “if she’d started dinner three minutes ago, we wouldn’t be in this mess” when Homer and Bart complain to Marge they’re hungry; that moment feels devastatingly real, when someone who’s an outsider tries hard to conform, adopting the same mannerisms and moans to make them feel compatible.

The integral scene is when Bart and Homer, on their knees furiously devouring squashed up chocolate, entice Lisa to follow suit, ravenously inviting her like a pack of dogs eager for a new cub. Lisa’s cry of “I don’t want to turn out that way…like you!” could have come across as harsh and condescending, but instead it feels like a sombre realisation. The irony is that throughout the episode, Lisa’s inquisitive search for DNA (leading to a hilarious Troy McClure skit), genes and puzzles shows a girl who’s intelligence was as robust as ever. The episode does give us a detailed detour into Lisa’s life, however, as she plunders thoughts into her diary, wrestles with her conscience and then gives her brain some final nourishment, taking in the high culture she enjoys before she resigns herself to “talk radio” and “vulgar mudflaps”. Does cleverness outweigh conformity, or can we live coherently without such intelligent pastimes? The show investigates this with aplomb.

Lisa the Simpson was the last episode of the Oakley/Weinstein era, a display of emotional depth that was simpatico with their seasons. At the end, Homer rallies up the Simpson men to show Lisa there’s hope in her future, but it’s up to Marge to save the day by proving the Simpson women all turn out okay. As a premise, it’s a little disappointing – Bart and Homer *are* smart, but in different ways, but in this episode they’re displayed as slack-jawed simpletons. Luckily, the ending is much more satisfying on a Lisa front, as it not only confirms she will keep her intelligence, but also shows that a lot of her DNA, even from her dad, isn’t such a bad thing to have, particularly his sweetness and compassion. As she cries out “woo hoo!” at the end (followed by a corrective “splendid”), it shows Lisa isn’t ashamed to be a Simpson, and that’s perhaps the smartest thing she, and other family outsiders, could discover.

“Your brain is the best friend you’ll ever have,” Lisa implores at one point. She’s not wrong, but it doesn’t have to be your only friend.