Four-year-old Gavyn Boscio loves to cook and asked for an Easy-Bake Oven for Christmas. But when his big sister went to buy one, she discovered to her disappointment that it comes only in girly pink and purple, with girls—and only girls—on the box and in the commercials. So the eighth-grader from Garfield, N.J., started an online petition asking Pawtucket, R.I.-based Hasbro to make the toy ovens in gender-neutral colors and feature boys on the package. By Friday, 13-year-old McKenna Pope’s petition had garnered more than 30,000 signatures in a little more than a week. And celebrity chef Bobby Flay, who...