While Kevin is watching TV, a closeup shows his arm on a table. When Karen and Louis come in, the angle changes to a long shot and Kevin is not near enough to the coffee table to have had his arm on it.
In one scene, Kevin is in the living room. He is watching a western movie on television. The broadcast is in color. Although in the USA color television began broadcasting in the mid 1960s, the Arnold family did not own a color television in 1968. In 'Christmas' (9) , the adult Kevin remembered that the family purchased a color television in the early 1970s.