Maybe the president who collected Spider-Man comics as a kid couldn’t resist the age-old face-off with a fly.

The moment had echoes of parables in which the ordinary one becomes the golden one.

In “The Karate Kid,” a teenager whose father has died learns lessons about the body and spirit from his surrogate father and karate teacher, Mr. Miyagi. His lessons are about not going to the dark side, the importance of discipline, and catching flies. “Man who catch fly with chopstick,” Mr. Miyagi says, “accomplish anything.”

In the Grimms’ fairy tale, “The Brave Little Tailor,” a tailor brandishing a rag kills seven flies swarming around his jam-smeared bread. The little man admires his own bravery so much — “For joy his heart wagged like a lamb’s tail” — that he wants the whole world to know of it. So he stitches up a belt for himself embroidered with the legend “Seven at one blow!” and saunters out.