Perhaps he was thinking about how loved up he is with his super hot girlfriend 90210 star AnnaLynne McCord, who he was seen snogging earlier on in the day.
Or maybe he’s just happy about the exciting direction in which his career is heading, the latest Twilight movie New Moon is released in a few week’s time and next year A Nightmare On Elm Street and Meskada both hit the big screen.
So really when you think about it there’s plenty of reasons for him to be smiling!