Actor Scott Speedman (TNT's "Animal Kingdom"); former "Bachelorette" Desiree Hartsock on her new book, "My Fairytale Wedding: Planning Your Dream Wedding Without Breaking the Bank"; animal expert Jack Hanna; Miss USA Olivia Jordan; Princess Diana's private chef, Darren McGrady, shares his memories; a preview of Robin Roberts' interview with R&B singer Bobby Brown on a special edition of "20/20," airing tonight on ABC.