Today on Twitter, Sean Kingston tweeted that his good buddy Justin Bieber was coming to visit him in Miami. We know Soulja Boy is hosting a big 21st birthday bash for himself in South Beach, so we're betting on the Biebs making an appearance! We just hope those three don't get themselves in too much trouble! Speaking of Soulja Boy, dueling rap queens Nicki Minaj and Lil Kim both tweeted him a happy 21st birthday. Nick Lachey and Sara Bareilles also tweeted that they were gearing up to begin shooting Season 3 of the NBC acapella competition, 'The Sing Off.' See what your favorite stars were chirping about today!