Today on Twitter, as Demi Lovato prepped for a hair appointment, she tweeted to ask her followers whether or not she's due for a new look. The 18-year-old superstar also spilled that she's glamming up for a party -- and we can only assume she means for her 19th birthday this Saturday, Aug. 20. Also in today's tweets, Cody Simpson gave his Twitter name a fresh makeover, Royce Da 5'9" put haters in their place, and Darren Criss bumped into his gorgeous fellow 'Glee' stars Dianna Agron and Lea Michele while shopping for a pack of gum ... Sort of. See what your favorite stars were tweeting about today!