Pop music's hottest artists including Carly Rae Jepsen, Taylor Swift, Nicki Minaj and Justin Bieber hit the 2012 American Music Awards; Skrillex and Skylar Grey celebrate the AMAs with Interscope; The Wanted performs for Joanna Krupa, Kendra Wilkinson and others at Us Weekly's Music Party; Nikki Reed, Brad Goreski, Jenny McCarthy and many more hit Rolling Stone's AMA after party; Joel McHale, Seth Green and numerous other comedians help Variety honor Seth MacFarlane—get the details on who turned up where during this very busy weekend in L.A. in this edition of Last Night's Parties.