And then there's Lou: rock steady, the man that keeps the whole thing going. He's fully aware of Wiggum's incompetence and is constantly angling for his job, going so far as to write letters to the editor of the Springfield Shopper (under the pen name "Worried in West Springfield") calling for the chief's resignation. Lou has no reservations about making fun of the chief to his face either, insulting his poor deductive skills and making fun of his ill-fitting pants.
He's the chef that looks like he jumped off the pizza box, constantly belittling his staff and conversationally berating his customers, doing it all with a misleading smile and sing-songy Italian accent. Being an asshole isn't confined to his restaurant, either: when Marge entered a cooking contest with her "dessert dogs," Luigi sabotaged her oven with "how do you say, malice of forethought." He's a complete jerk, but he comes off as lovable because he sounds happy and he's kind of roly-poly.
He pops up in episodes here and there. During the Springfield Mayoral recall election, Luigi threw his hat in the ring, promising to "make you the good government, just how you like it." Luigi's character works because he's used often enough that you know who he is, but sparingly enough that his "Italian chef as Italian stereotype" act and his being a total dick don't get stale.
But in the end, there's only one thing to know about Luigi: his English isn't bad because Italian is his first language. He doesn't even speak Italian. Luigi's first language is "how do you say, fractured English. It's what [his] parents spoke at home."
Bart and Homer are the crowd-pleasers, no arguing that: their misadventures dominate the show, and their faces hog the merchandise. But it's Lisa, the second-grader reading at a 14th-grade level, who is the heart and soul of both the family and show.
We love Lisa because she yearns for something greater. She wants to better herself, her family, her town. Sure, she's a nerd--who among Simpsons fans isn't? And without this little overachieving genius and hopeless do-gooder saving the day (on a weekly freaking basis!), our favorite family would've been killed a dozen different ways, the town of Springfield would've been destroyed, the very earth itself lost.
Let's hear it for Lisa! Nobody's favorite character, but the most UNDERRATED SPRINGFIELDIAN OF THEM ALL.
For an obscenely long rant on the lovable lil' Lisa's underrated quotient, check out the Underrated blog here.