Definitely Invader Zim.
It got canceled because of stupid overprotective parents that when they come in and see something that looks like it's covered in blood immediately have their entire state flood the producers with rage.
The "Bloody Gir Incident" was nothing but a gigantic misunderstanding, but no. Parents are ignorant and stubborn and refuse to hear people out when they say "just watch the whole scene, it's only ketchup."
Hell kids that actually watched the whole scene would have seen it as ketchup and not blood because unless the kids are like the rest of the 80% of the American and European minor population that are under 10 and have already seen at least 50 R rated movies and swear more than a drunk scot, they wouldn't even have it come to mind until they were 30 that it was blood.
For those who don't know, Invader Zim was an incredibly brilliant cartoon that was canceled because in one scene, all hell was breaking loose and Gir (the best character in the series) was holding a bottle of ketchup which then exploded, moving to a view of dark evilness as we see Gir covered in slow moving red liquid with a soulless look on his face.
God damn.