My goddaughter is 2 and my girlfriend's nephew (who've I spent considerable amount of time with) is 4. The goddaughter watches may more TV than the 4 year old but both watch a couple of hours a week. I've only seen them view animation videos on youtube that seem like in days gone by would air on PBS.

I'm not sure what kind of parent would let their kids watch stuff like this but it's pretty shocking to see that this stuff is even marketed as "for children". The only "for children" things I've seen on Youtube are pretty innocent animated shorts (lots of nursery rhymes too). But I guess the algorithm will show you what it thinks you like.