I just watched "the worst episode of The Simpsons", as voted by the most notable fansite for the show. The episode is from season 11 and is called Kill the Alligator and Run.
That website is full of shit.
Now, I have extremely limited experience with The Simpsons after season 9. I've watched all of the first nine seasons multiple times. Even without seeing the other hated episodes, like the "jockey elves" episode or the Lady Gaga episode, I can tell you that Kill the Alligator and Run is absolutely 100% not even close to being the worst episode, even if we throw out every clip show episode. (I hate clip show episodes on principle but that's neither here nor there)
I'll start with the bad:
The main point of the plot is dumb. The Simpson family goes to Florida, and Homer accidentally kills the town's beloved alligator. Except it's revealed at the end of the episode that the alligator didn't actually die.
And I get it, the "alligator is still alive" thing came out of nowhere and undermines the last ten minutes of the episode. There is no lead-up, no hints, nothing. The alligator stumbles out of a random building for no reason, and all is well, but not forgiven. Whatever. It makes no sense at all, but it doesn't completely ruin the episode. It's a bad ending to an otherwise very good episode. (I also don't like the "banned from nearly every state" jokes at the very end but that's a minor nitpick)
Aside from the ending, the other bad part of the episode is the Kid Rock segment. Homer finds his way to a Kid Rock show, and "ruins" it. (I'd rather listen to Homer sing We Built This City than a Kid Rock song but that's just me)
Honestly, it's pretty easy to improve that section. Kid Rock says that he wants to pour out a 40 for his homeboys, but 40 ounces isn't enough, and produces a 40-gallon bottle of liquor. Homer is instantly on-stage, drinking the liquor, then grabs the microphone and begins singing We Built This City.
It would have been improved if Homer realised that they were going to pour that liquor on the faux-curb, and decided that wasting that much liquor is sick and wrong. He'd drink the liquor for that reason, then get carted off without the We Built This City. We Built This City also shouldn't have been reprised not once but twice during the episode.
Now for the good:
This episode has some really fucking good jokes. Not every single one lands, but I was laughing throughout.
I recommend actually watching the episode, but if you don't want to, here's the highlights:
https://youtu.be/frlWocgo6HA?t=29
https://www.youtube.com/watch?v=-tlXkILR51M
https://www.youtube.com/watch?v=3IdMYxg8_ew
Overall, the episode gave me some good, hard laughs, and some nice, sensible chuckles throughout. It's a shame that the main plot of the episode is so nonsensical, but I don't think it lets this episode down too much. It's not the fucking worst episode in the series by any stretch of the imagination.
So what is the worst episode I've seen, you ask? It's Lisa the Vegetarian. The Principal and the Pauper is second.