It could've possibly aired on Adult Swim, the block did air for a period on the French feed of Cartoon Network, which is available in Switzerland. Maybe this could've been an ad for a movie? The Saw films did some odd commercials back in the 2000s.
I will follow this hint as cheeseplanet suggested too but didn’t AdultSwim aired partially on Cartoon Network more in the night ? Because, when the screamer ad event happened it was like around the early afternoon. But maybe it was a broadcast mistake ?
I wouldn't rule the possibility of this being a broadcast mistake, as Cartoon Network in the UK at one point did accidentally air a betting commercial (somehow). So I could see this ad/thing airing on accident on Cartoon Network