...the knowledge with them that Japanese and Chinese people have eyes that slant in opposite directions ...
What???? First I've ever heard that.
I have, but
only as unthinking, cruel schoolyard humor. A child, usually with no observable Asian ancestry, would say, "My father's Japanese," and raise the outer corners of his eyelids. He continue with, "My mother's Chinese," and lower the outer corners of his eyes. He'd finally follow with, "And I'm both," while raising one outer eyelid and lowing the other, usually while crossing his eyes.