I'm stunned. This was a quality episode. And it follows another pretty good episode. I wonder if they can keep this up. This is the kind of show I was hoping the movie would lead to, in terms of the writers stepping it up a notch.
I mean, the difference between this and just two weeks ago, "Homer of Seville", is incalculable. Every time I expected them to trade the story's integrity in for a dumb gag, they didn't. (Well, the ending was a little bit lame.) I was wary about the musical montage of the prisoner stalking Marge, but it paid off with a good Moe gag and the tone shifted appropriately back to suspense afterward.
The new character was also very likeable, and his pathetic nature led to quite a few classic Simpsons gags. My favorite would have to be where he crawled out of the prison waste tube and then saw the mountain spring water tube right next to it. It's not a totally new joke, but it was executed well, playing off the dark ambience of the scene leading up to it.
In some ways the plot is too much like "Pokey Mom", but this episode really is much better. So I have no complaints about it.
Honestly.