The scares weren’t just on the screen at the premiere of Elizabeth Olsen’s horror flick “Silent House” Tuesday. “There was a mouse rampaging around the theater,” said a guest at a Stone Rose bash following the AMC Loews Lincoln Square screening. “It ran up the aisle, towards me, during the movie, then headed to the exit.” No word on whether the rodent made it all the way to the after-party with Mary-Kate Olsen and Russell Simmons, who was seen chatting up Sky Nellor and a tall brunette. Lizzie (“the other Olsen”), in a sparkly jacket and Piaget jewels, briefly left her fete when she heard “Boardwalk Empire” star Jack Huston was next door at Porter House with his aunt, “Smash” star Anjelica. “We’re shooting a movie together Monday and we’ve never met each other,” Huston was overheard explaining when Olsen — who has six upcoming films — arrived. Across the room, Liam Neeson and gal pal Freya St. Johnston had an intimate dinner before she headed to Europe. An exec behind “Silent House” (out tomorrow) sent Neeson a bottle of Pinot Noir to toast the box-office success of his latest, “The Grey.”