Planned Parenthood's sex ed chatbot, Roo, lets teens anonymously ask questions about sex, relationships, puberty and more. Roo's success (3.5 million conversations in 9 months) stems from a theory-based, judgment-free product and marketing strategy. In this talk, get a glimpse at the design of our bot —tone, UX, ethical AI— and companion YouTube series. Attendees will learn how to utilize behavior change theory to inclusively design relevant, engaging, and useful products for young people.