My favorite is Lisa, especially when her self-righteousness falters a little.
As for favorite quote, there are way too many - our family uses them as shorthand. Today, I think it may be, “I have misplaced my pants.”
Remember the episode back in the '90s where Marge gets arrested for shoplifting after Maggie puts something in her pocket?
Nelson approached Bart on the playground:
Nelson: HA-ha! Your mom’s a jailbird!
Bart: So’s yours.
Nelson: Oh yeah! Let’s play!
Another favorite was a scene where Abe Simpson is walking down the street with his bearded friend, and they’re accosted by a young man asking for a handout. Abe yells something like, “Get a job, you bum!”, then starts ranting to his friend about how, “In our day, we WORKED for everything we got! These kids today just want everything handed to them!”
Immediately after that speech, the two seniors turn into the Social Security office, where Abe starts banging his fist on the counter and shouting, “I’m old! Give me money!”
the show does such a good job giving a character a personality type that can be played on. there can be elements of multiple characters that can be related to; nonfamily characters can be fairly stable like Frink, Skinner or Comic Book Guy family characters can be more dynamic.
best quote
In this house, we obey the laws of thermodynamics.
Another vote for lionel hutz.
Greatest line? That’s a paddlin.
Side Show Bob
Line: “I’ll be eating food tonight!” (Old Gill.)
Ralph, 
I eated the purple berries 
It tasted like burning
Fat Tony, “I don’t get mad, I get stabby!”
Homer, “Yes, Lisa. A wonderful, magical animal from Happy Land!” (The whole conversation, really)
Favorite character is Professor Frink. Claiven noiven, indeed!
Best character? Tough but I’ll go Moe.
My fave lines are all lies.
"I believe it was a boaking accident.
By the many arms of Vishnu, I swear it is a lie.
I’m not sure whether he actually lives in Springlfield, but my favourite character is Krusty, with all his backstories from the wars of showbiz. My favourite line is:
"I ought replace it right now with a Chinese cartoon where robots turn into blingwads!
But I’m a lazy, lazy man, Roger. So I’m gonna give you one more chance."
I’ve always loved that one too and the next part
“If I had a gun, I’d shoot you!!”
Employee: Well, you don’t.
Ralph: (crying, after being pepper sprayed)
“Even my boogers are spicy!”