10 Greatest Unspoken Sci-Fi Movie Plot Points
4. R2-D2 Disobeys Luke Because Of Anakin - Star Wars: The Empire Strikes Back
In The Empire Strikes Back, you'll surely recall that R2-D2 (Kenny Baker) isn't one for obedience. When Luke Skywalker (Mark Hamill) insists that he remain with the ship, R2 refuses and follows his charge.
At the time of Empire's release this simply seemed like R2 being an adorably loyal bot who knew when Luke needed help but perhaps couldn't ask for it.
But in light of the prequels, R2's defiance is viewed within an entirely different, more tragic context. The catalysing incident seemed to occur in Revenge of the Sith, when Anakin (Hayden Christensen) lands on Mustafar with R2 and insists the droid stay with their ship.
R2 obeys, but of course, Anakin subsequently fights Obi-Wan (Ewan McGregor), gets horrifically injured, and is transformed into Darth Vader, ensuring he never returns to R2.
As such, we can firmly deduce that R2 developed some understandable attachment issues, and by the time Luke tells him to sit tight decades later, he's not going to be left to his own devices once again.
Obviously in reality this was really a case of George Lucas reverse-engineering the plot in non-chronological order, but it still slides together quite perfectly.