I can't remember the last time that I laughed so hard while watching a single episode of The Simpsons. Especially in the first part.
The story begins by an earthquake in the Simpsons' neighborhood. But it's not a quake: all of the airplanes are flying above the houses around. It appears that the main run has been changed. We eventually discover that mayor Quimby changed it because he wanted to hear his wife's voice (a choice he quickly regrets).
Homer and Marge complain about the situation to the Congress representative, but he dies. So the State needs a new one. Bart suggests Krusty the Clown. The clown accepts and becomes the Republican candidate.
The first part is incredibly funny. It all begins by a vintage episode of the Three Stooges, followed by a fake FOX promo that Homer eats like chips. It's so special. By doing this (and later by scrolling fake newsroll), FOX has the great capacity of spoofing itself, something that other major networks aren't necessarily able to do.
The second part is still funny, but it's not as hilarious as in the first one. You may have guessed that Krusty wins the election...
Then it turns into a fish-out-of-water comedy and into a political satire. Politicians are depicted as incompetent, vote useless and ridiculous laws and scandale-makers.
A last hilarious moment: Homer can't lead Yogi Bear to the maze exit...