Complex sentence: The story centres around two alien agents, Cadet Flynn and Psuedo-Cadet Niven, who are in fact incredibly advanced and evolved vegetables on an information finding mission to Earth, where they take on human form.
Split into simpler sentences: The story centres around two alien agents, Cadet Flynn and Psuedo-Cadet Niven. They are incredibly advanced and evolved vegetables on an information finding mission to Earth, where they take on human form.