In this episode, Liz and Sarah share the (surprisingly strong!) listener reactions to the IgG food test that led to Sarah going gluten-free. Then they invite Happier's Gretchen Rubin (also known as Liz's big sister) to help them solve the age-old writer problem: How do I get myself to write? Gretchen breaks down her trademark Four Tendencies and explains how understanding your tendency can help you achieve your goals. Liz and Sarah debate the merits of plastic surgery and Liz reveals a secret that even her husband doesn't know. They also share a life-saving Hollywood Hack -- have an emergency kit! -- and reveal their latest celebrity sightings.