Why Do Children Love This Terrifying Stuffed Animal They Have to Hatch From an Egg?

"Hatchimals" were the Tickle Me Elmo of Christmas 2016, the kind of uncanny gotta-have-it stuffed animal that children demanded while the rest of the world looked on in horror. They were small, brightly colored robotic creatures that kids were supposed to coax from eggs and then "nurture," though they remained in a state of permanent adolescence.