When Kane and co. come across the iconic Space Jockey remains inside the derelict ship, Ridley Scott used the scene as a chance to allow his two young sons to appear in one of the most iconic sci-fi movies of all time. Or rather, he used his sons' smaller stature to accentuate the sense of scale he was going for in the scene. In many of the wide shots where the crew's faces can't be seen, two of the actors are Scott's own sons, largely because they would look even more dwarfed by the Space Jockey than an adult actor would. The results, of course, speak for themselves, and it's a shame that Scott didn't stick to this scale difference when dealing with the Space Jockeys/Engineers in Prometheus.