The proud declaration “We Make Toys” is painted in giant letters, in the signature ruby-red color of Mattel’s logo, at the top of all buildings in the company’s complex in El Segundo.

It’s in the hand-painted eyelashes on every Barbie doll prototype. It’s in the meticulous detail found on the millions of Hot Wheels and Matchbox cars made every year. It’s in the ingenuity of the ...