Celebrity Pictures: Lady GaGa, Rihanna, The Duchess

Today's celebrity pictures include a green-haired Lady GaGa doing her mother monster pose as she arrives at the Park Hyatt Hotel Down Under.

Over in the US, a casual and inconspicuous Rihanna is spotted out and about in Brooklyn, and cleavage-exposing reality TV star Aubrey O'Day arrives for 'Rehab' Sundays at the Hard Rock Cafe in Vegas.

Meanwhile, presenter Ellen DeGeneres and actress Portia De Rossi enjoy a romantic stroll as they holiday in Portofino, Italy, and Vampire Diaries star Ian Somerhalder attends the Bloodycon Fair in Vienna, Austria.

In the UK, Elton John and Tinie Tempah chat on the front row of the Richard James Catwalk Show, London, and Pixie Lott performs at Chester Rocks Festival. And the Duchess of Cambridge visits the 'Expanding Horizons' Primary school camp at Margaret McMillan House to meet inner-city children as they experience the countryside for the first time.