This week, we’re listening back to one of our all-time most popular episodes. Evolutionary biologist John Logsdon explains the amazing diversity of sperm design, and its connection with mating behaviour. And Scientopia blogger Scicurious discusses some of our favorites from her Friday Weird Science archives, covering everything from the antidepressant properties of semen, to smelly semen, to testicle receptacles, and much, much more.