When Benny walks into the house at the beginning, you can see that she has a cigarette between her index and middle fingers on her left hand and puts it in her mouth. Then, in the next shot, the camera pans over to her left side and you can see that she doesn't have a cigarette in that hand or in her mouth.
When Randy, George, Amy, and others are in the bar, as Randy is sitting down, the whipped cream on Randy's face varies from shot to shot.