In an outdoor enclosure, two juvenile black-footed ferrets pounce and somersault, tumbling over each other in a playful fight. The loser breaks free and rushes into a tunnel lined with a plastic tube.

Riri Williams, a young black woman who dons a version of Iron Man’s armor to become Ironheart, was a 2016 creation by Brian Michael Bendis, who is white. But in 2018, she was reimagined by Eve ...