The Transformers star is off and running during a workout in L.A. Plus: Ashlee Simpson-Wentz, Brad Pitt, Britney Spears and more

FACE OFF

Who's that girl? Lady Gaga hides her poker face on Tuesday during an appearance at a press conference in Floriana, Malta, where the singer was set to perform – along with the Black Eyed Peas and Metro Station – at the Isle of MTV concert on Wednesday.