Author and Illustrator Gene Luen Yang remembers vividly the “birthday bird” from one of Dr. Suess’s books who told the main character that in addition to all the presents and cake he receives on his birthday, he should be grateful he wasn’t “a wasn’t”—someone who did not exist. That bit of existential terror stuck with the author. Superheroes like Peter Parker, who had a tough civilian life but who could still be heroic, and Superman, the ultimate immigrant who has to navigate between two cultures, also made a big impact on Mr. Yang as a child and still as an adult.