Pepper Potts and Tony Stark reunited in Pasadena yesterday as the cast and crew got to work on Iron Man 2 . Both Gwyneth Paltrow  and Robert Downey Jr . slipped back into their familiar roles with ease — RDJ even carried an Iron Man  lunchbox with him on set. Director Jon Favreau  excitedly twittered about how excited he was  to get back to set and see his chair waiting . Robert celebrated his 44th birthday in LA  over the weekend joined by friends Reese Witherspoon  and Jake Gyllenhaal  as well as Favreau and Gwyneth which sounds like the perfect way to kick off work on the eagerly anticipated film.