Today on Twitter, Demi Lovato unleashed some big news: she's going to sing the National Anthem at the World Series! Whether you're a baseball fan or not, you'll want to tune in to catch that once in a lifetime opportunity. Maybe she'll even pitch a few? Also in today's tweets, Lea Michele teased, but didn't spill, some big 'Glee' news, Adam Levine cried crocodile tears for basketball, Sara Bareilles sang an ode to Britney Spears and Bruno Mars sought a little Halloween costume help. See what your favorite pop stars were tweeting about today!