Chowder- When I first saw the previews, my assumption was that this show would be another Whatever Happened to Robot Jones?-a mediocre cartoon with cheap animation. And when I saw the premiere, I thought that it was mostly just weird, but a few episodes later, Chowder started to grow on me. To update this story, Chowder is currently one of my favorite shows on CN. I now think that Chowder is funny and weird, but in a good way. I especially like the characters of Mung Dahl and Truffles.
Ed, Edd 'N' Eddy- Becasue this show came from Danny Antonucci, the same man who gave us The Brothers Grunt, my expectations were considerably low, but the Eds really started to grow on me after a while, even though I didn't enjoy the last couple of seasons as much as I did the earlier ones.
Johnny Test- When JT premeired on Kids WB, I thought that this was the single stupidest cartoon ever made. Ironically, I didn't start to appreciate Test until after the reruns began airing on Cartoon Network. Test still isn't one of my favorite shows and CN runs it way too much, but I enjoy it more now than I did when it first aired.