I figure that this requires a post. Bloody GIR was the first recognizable instance of interior censorship by a channel. Basically, there was supposed to be an episode where GIR appeared covered in blood. When it was submitted to Nickelodeon for approval, it was shot down. From what I can gather, it was supposed to be from the series finale. So what the writers, directors, producers and everyone else involved did was they put the image of "Bloody GIR" in one frame per episode for the entire second season.
So Yea... That's that.