Invader Zim; Brilliant show. Funny, not any subconscious learning going on in the background. Not a bit of, "Hey, let's try to string a plot together through the course of the show." Gir was the greatest thing to hapen to TV; ever.
Firefly; I only ran across this one recently; I have heard people talk about how great it is, but never seen it for myself. So I finally watched it. I was almost through the first (last) season before I learned that the show was doomed to only one season. Argh. I wanted to find out the Sheapard's secret history.