In the scene where "Tess" (Julia Roberts) is first introduced in the movie, "Russ" (Brad Pitt) is eating shrimp cocktail. Notice the dish -- it's a large glass. When the shot moves to a different angle, the shrimp is suddenly on a plate. The shot changes again, and the shrimp is once again in the glass.
If you play the movie with the commentary on they say that they had to re shoot this scene because they changed what Julia Roberts was wearing so that is why the dishes are different...granted they should have paid closer attention to this because in my opinion it was a very noticeable slip up