This absolutely terrifies me. That character is so incredibly creepy, and the things it's encouraging kids to do is even creepier.
Parents, PLEASE monitor what your kids are watching! This new "Momo Challenge" hacks into the middle of even the most kid-friendliest of content (Even on YouTube Kids)! The creepy character will tell kids how, and encourage them, to harm themselves.
While YouTube says they are working on new technology to assist parental controls and find this type of content faster, it's still important that you are in tune with what your child is watching. These videos are still slipping in despite parental controls.