Young adult, beloved author John Green appeared on CBS’ The Late Late Show with Craig Ferguson last night to talk about his hit book The Fault in Our Stars.

Ferguson, who’s a fan of Green’s latest, touched on Team StarKid (Joe Moses was apparently in the audience), Harry Potter conferences (seemingly making a reference to LeakyCon), and more.

Green’s appearance begins at 28:30 in the episode, which you can watch below…

Yesterday was a big day for fans of The Fault in Our Stars. The book to film adaptation of Green’s young adult novel cast Shailene Woodley in the lead role of Hazel Grace. “I am absolutely thrilled that Shailene will be playing Hazel in The Fault in Our Stars,” said Green about the casting decision. “It means a lot to me that she is a fan of the book, and I know from our conversations that she has a profound understanding of Hazel. Watching her audition, I felt like Hazel Grace Lancaster was talking to me. It was eerie–and very exciting.”

The film does not yet have a release date or an actor to play Gus, but we’ve heard from sources that Shameless actor Cameron Monaghan is one to watch.