[Pharaoh] said: "You people are lazy. Lazy! That is why you say 'Let us go sacrifice to God'." (5:17)
"I'm shocked - shocked! - to find that gambling is going on in here!" (Casablanca)
This line of Pharaoh's reminds me of a famous cinematic line which uses the same literary effect. In each case the speaker, an authority figure, could have left out one word, and thus made a grammatically correct sentence saying what he wanted to say. But both times, the speaker instead repeats the key word representing his feelings about the situation. This has two effects: 1) the emotion is intensified, and 2) the speaker expresses scorn towards the subject. You can imagine Pharaoh saying the word "lazy", and then repeating it, slowly and condescendingly, while Moshe absorbs the resulting humiliation. By adding just one word, the laconic story of the demand's rejection is transformed into a vivid scene which shows exactly what Pharaoh and Moshe were thinking at the time.
This is the sort of cool little narrative touch which is easy to miss, but which makes the biblical story much more vivid and fun if you get it. Of course, though, Sefer Shemot does not have the funny punchline which reveals that the Captain Renault's outrage is in fact hypocritical and feigned.