Shameless flirt Julia Roberts has been cozying up to Sean Penn even though her long-suffering husband, Danny Moder , is not happy about it – and pals confirm he's got every reason to watch his back, RadarOnline.com can ​​reveal. Her most recent film, After the Hunt, was a bomb at the box office, while Penn's One Battle After Another has been a huge critical and financial success. So it was natural for her to turn to her longtime friend and neighbor for advice and consolation. "Sean and Julia speak their own language to each other, which can even get physical at times, with flirty body language, and Danny is definitely an outsider to that dynamic," said the source. And when somebody of Penn's stature wants to be a sounding board for Roberts' worries and complaints, Moder doesn't have any choice in the matter, said the source, before adding: "Sean offers something to Julia that she's not getting at home with Danny, and Danny just has to accept it."