Kryptonite

Via the November 13, 2006, episode of The Writer's Almanac, a poem of the same title by Ron Koertge in Fever:

Kryptonite Lois liked to see the bullets bounce off Superman's chest, and of course she was proud when he leaned into a locomotive and saved the crippled orphan who had fallen on the tracks. Yet on those long nights when he was readjusting longitude or destroying a meteor headed right for some nun, Lois considered carrying just a smidgen of kryptonite in her purse or at least making a tincture to dab behind her ears. She pictured his knees giving way, the color draining from his cheeks. He'd lie on the couch like a guy with the flu, too weak to paint the front porch or take out the garbage. She could peek down his tights or draw on his cheek with a ball point. She might even muss his hair and slap him around. "Hey, what'd I do?" he'd croak just like a regular boyfriend. At last.