During the flashback when Ted tells Barney and Marshall about the girl with crazy eyes he dated, Janine, she smashes a car windscreen with a pipe but when the camera changes the windscreen is not smashed.
During Ted's flashback, when Lily sneaks back into the apartment to move the picture, there is already broken glass on the floor, but when Lily moves the picture, and is then startled and drops it, the glass has gone, and the picture smashes as originally intended.
Scott places Marshall's cup on the counter making a noise that the cup is clearly empty.