Last year, Roman Mars teamed up with Hank Green to guest host Dear Hank & John -- this year he's back on the Greens' show once again, but this time with Hank's brother John Green (Turtles All the Way Down, The Fault in Our Stars, The Anthropocene Reviewed).

In their podcast Dear Hank & John, "hosts John and Hank Green (who are also best-selling authors and pioneering YouTubers) offer both humorous and heartfelt advice about life’s big and small questions. They bring their personal passions to each episode by sharing the week’s news from Mars (the planet) and AFC Wimbledon (the third-tier English football club)."

This week, guest host Roman Mars joins the show to discuss things like: Are roaches a moral failing? How do they do surgery on a fish? Why do only old people like stinky cheese?

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WHAT TO DO WHEN THE WORLD CHANGES - S04E05