Celebrity pictures: Katy Perry, Russell Brand, Lady GaGa

Today's celebrity pictures include a bra-flashing Lady GaGa leaving her hotel in New York, and British comedians Russell Brand and Noel Fielding attending Amnesty International's Secret Policeman's Ball at Radio City Music Hall.

Meanwhile, Joel McHale arrives for a screening of NBC's comedy series Community as part of PaleyFest 2012 in Los Angeles, Reese Witherspoon attends church with her family and Entourage star Jeremy Piven plays with band Bad Decisions in Las Vegas.

In Paris, a blue Katy Perry, a sultry Kristen Stewart and a wet P Diddy attend the capital's Fashion Week, Kylie Minogue arrives for a Mardi Gras 2012 after-party down under in Sydney, and Prince Harry acts as the Queen's ambassador as part of her Diamond Jubilee year in the Bahamas.