I agree with Pride of Staten's must-see's, and I'm curious about people's take on the last 7 or 8 episodes of ATHF. I don't tend to be too critical, but i thought they were awfully unfunny.
I hated ATHF first few times I saw it (over holidays. My father and little brother are crazy about it.)
But I went through every episode recently, and I love the show immensely.
Part of the enjoyment came when I started reading the ATHF as outcroppings of the Lovecraftian universe. The "monsters" are like Old Ones, but zany. And maybe that's what Lovecraft needed: more zaniness! What's scarier than monsters? Monster's with random, unmotivated humor (like the onion-spider and his JUICE or the dimwitted aliens.) There's also something to be said about the consistent use of "the industrial world" as gags: for example, Shake with his back hoes/burning tires, Frylock's cloning experiments and naive scientism/modernism. I also think it's neat that Meatwad sort of 'grows up" and has switched affinity from Frylock to Shake (who now seems to like Meatwad.)
Whenever I try to describe ATHF to someone, I say that it's a cartoon about hell. And I think that that's the point or at least the frame of reference (if you can find one in their universe.) I laugh my ass off at most every episode, but feel really gross afterwards too (like the one where Shake eats the "cherry pie" in the bathtub.)
Just some random thoughts.