Michelle Williams and Sarah Silverman slipped into red and white swimsuits to shoot a scene for Take This Waltz in Toronto yesterday. While in the water Sarah slapped Michelle's bum as she climbed out of the pool, resulting in lots of laughter. Their costar Seth Rogen wasn't there, but has had his share of fun scenes with Michelle already. She'll be reunited with her Blue Valentine costar Ryan Gosling at the Toronto Film Festival in September.