There is a brief glimpse of male genitalia in Golden Boy at the Belasco Theatre on Broadway. It comes toward the end of the second act. There’s a scene set in the locker room. One fighter complains when a woman walks in and she says something like, “If you’re modest close your eyes.” He’s fully clothed and the scene goes on. But way upstage on the back of stage left (audience right) another boxer strips to his jockstrap, then pulls that off and then wraps himself in a towel to go to the showers. It’s very brief and hardly noticed with everything else going on, but if you see it, you see it.