"201" - South Park
Yes, South Park has always been problematic, but never so much so that an episode was wiped off the grid... except for this one. Episode "201" is a notorious two-part episode that depicted the prophet Mohammed along with other religious figures. In religion, depicting Mohammed in any way is considered blasphemous. This episode sparked rage in a lot of folks. The animators tried hiding the figure in the second part (pictured) but they only made it worse.