Joan Jett, Alison Mosshart, and other rockers ring in the 2013 Sunset Strip Music Festival at House of Blues; Kelly Osbourne, Lauren Conrad, Lance Bass, and many more step out for this year's Young Hollywood Awards; Kendra Wilkinson and Jessica Hall show their support at a charity event hosted by Playboy Radio; Minnie Driver and Christopher Wolfe attend the I Give It A Year screening; Demi Lovato, Diane Kruger, Zooey Deschanel and other network stars go to the FOX All-Star party; Simon Cowell, Kelly Rowland, Andy Samberg, Minka Kelly and more field questions at Day 9 of the Summer TCA Tour—let us give you a peek inside all of Thursday's top events in L.A. with this edition of Last Night's Parties.