Continuity mistake: During the scene where Viola and Charlie are talking about the wedding plans at lunch, Viola has her glasses off, in her hand. When Charlie says "being that I'm more spiritual that religious," the glasses jump back onto Viola's face between shots. She then removes them, and leaves them off, however after she pulls out one of Charlie's hairs, they reappear on her nose again.
Other mistake: During the scene where Charlie is watching the horror movie on TV and Viola sneaks up behind her wearing the costume with the long finger nails and scares her. They show a shot from Viola's point of view and you see Charlie sitting on the couch from the back, but the TV is not on.