Ironically, Invader Zim was canceled because the execs at Nick found the show "too dark for children." This, after they hire Jhonen "Johnny the Homicidal Maniac" Vasquez to animate it, because they wanted a show that the older kids could watch.
On-topic, besides the previously stated, there was a little-known show on the Sci-Fi Channel called "Jake 2.0". Lasted less than a season before getting scrapped. Great show, but then again...little-known. I guess they wanted a show that 100 million viewers watched with mediocre ratings, rather than a show that perhaps 10 million viewers watched that was well-rated.
On-topic, besides the previously stated, there was a little-known show on the Sci-Fi Channel called "Jake 2.0". Lasted less than a season before getting scrapped. Great show, but then again...little-known. I guess they wanted a show that 100 million viewers watched with mediocre ratings, rather than a show that perhaps 10 million viewers watched that was well-rated.