ROBERT PATTINSON and KRISTEN STEWART attended a Halloween party Wednesday night wearing those creepy transparent masks. 

Meanwhile, Kristen's side-action RUPERT SANDERS went trick-or-treating with his estranged wife LIBERTY ROSS and their two kids. 

 By the way, Rob, Kristen and TAYLOR LAUTNER sat down for that live interview with MTV last night.  It was pretty boring because no mention whatsoever was made of Kristen's affair.