Mine’s gotta be Marge on the Lam. It’s got Ballet as bears driving little cars, it’s got Homer about to have his arms sawed off cause he didn’t let go of soda, it’s got good waffles sticking together, it’s got moonshine straight from your own still, it’s got ghost cars, it’s got Miguel Sanchez, it’s got Sunshine and Lollypops and Raibows, it’s got precious antique cans, it’s got suspects in a…red car who are passing directly beneath the earth’s sun…now. it’s hilarious and really encapsulates season 5s ‘fuck it, we ball’ attitude.
This might be my choice too. There’s a sort of serene quality to those early episodes that they never quite managed to reach again (and probably didn’t try to).