Invader Zim is amazing; went into it knowing little except from the enthusiastic recommendation of others. Wonderful animation, of an unheard-of quality in Nickelodeon (which is usually on the level of Hey, Arnold or Rugrats--at least Spongebob Squarepants makes the crude animation part of its loose-limbed sense of humor).
And the comedy--it's not so much the dialogue that is funny, it's the characters and the setup: megalomanic alien (Zim) and monomaniac Earthling (Dib) clash, resulting in literal, metaphorical, and comical sparks. The plots are funny and inventive and often surprisingly gruesome (some of my favorites include 'Nanozim,' where Zim enters Dib's body as a microbe-sized invader, ' 'Hamstergeddon' where a cute hamster grows to Godzilla proportions, and 'Dark Harvest,' about organlegging), but really, it's the way both alien and Earthling shriek and snarl and howlingly declare the power or hopelessness of their respective situations that is so consistently funny.
Sympathy here is a rather slippery concept--you don't want Zim ending up on a government autopsy table, the same time you don't want the Earth to be invaded--and Vasquez manages to sustain the ambivalence surprisingly well. He also wheels in a plethora of engaging side characters--Gir, a combination of cute puppy, annoying sidekick, and insatiable glutton; Gaz, a Wednesday Addams with a book or video game grafted to one hand; and Mrs. Bitters, a schoolteacher with an outlook on life sunny enough to make Olaf Stapledon look like Mary Poppins.
There's just a hint, an intriguing one, of pathos in both their positions: Zim is literally the only one of his kind on Earth, and handles his loneliness with enormous helpings of bluster and denial; Dib is literally the only one on Earth who knows about Zim, and is dealing with his loneliness in an equally unconstructive manner.
Some notes: Maybe it's just me, but is the flying pig in one of the episodes a homage to Miyazaki (he loves pigs, and he loves flying)? The aerial sequences look just a tad familiar...
Like I said, went into it knowing very little; came out a confirmed fan. Blockbuster Video marked this "PARENTAL GUIDANCE:" necessary warning for softheaded kids, I suppose.