I love that show, especially the ones that they made before Tarkovsky left the show ("Libretto" is definitely a favorite episode, along with the one with el Chupacabra [Dee Dee: "If you made him to scare me, then why does he eat goats?" Dexter: "I never said it was a completely successful experiment..."]). The ones made after that were just weak, both in animation and writing I think.
The little sub-shows they'd have were hilarious, like Dial M for Monkey and Justice Friends (Vallhallen, the Viking god of rock, was awesome: "Ahh! Help me! Help! There's a bee in my hair! Oh, there's a bee in my golden tresses, oh please, get it out, get it out..." *sobbing*). Their parodies were the greatest. I remember there being an episode of the main cartoon that parodied that old show Speed Racer that was just too funny.
Tarkovsky has created some great cartoons; between Dexter's Lab and Samurai Jack, I'm not quite sure I could pick a favorite.
"I am...RATMAN!"