Where do three singers go next after they've all sung in Las Vegas' longest-running musical, 'Phantom of the Opera'? The answer for three of them is to sing as The Phat Pack. Although the name alludes to Sinatra, Martin, Davis and the rest, these cats are a different breed. They sing classics from musical comedy, American standards and a few of their favorites. The Phat Pack performs at Cabaret Jazz at the Smith Center this weekend.