Basically there are thousands of videos on youtube targetted specifically towards young children, with titles and tags like "SPIDERMAN ELSA PRANK." They usually have live action actors of people in costumes and a good chunk of the videos do depraved shit like simulating scat fetishism, mutilating people, sexually assaulting people, etc. The reason it's such a big problem is that these videos slip past any filters youtube has in place, and are even on the YT kids app. Most parents aren't aware of these because all the sounds are just copyright-free music and stock sound effects, so if you aren't watching every video then you wouldn't know anything is wrong. And the videos autoplay so if you set them up with a video you've seen then it will just keep playing recommended videos until a fucked up one comes up. The weirdest part is that tons of them get millions of views within a day of being uploaded. It's basically bigger than pewdiepie level popularity for a bunch of mind-numbing content of people dressed in Disney-copyrighted characters, but Disney does nothing about it even though a lot of the vids make ad revenue off millions of views. Some have been demonetized but a good chunk of them aren't. Flagging the videos does nothing.

https://www.youtube.com/watch?v=jQRetpuZI1Q
https://www.youtube .com/watch?v=sP829Ky1KIk
https://www.youtube .com/watch?v=FME1rxd_qaI