The two currently extant "Star Wars" trilogies contain intentional points of resonance that serve to strenthen the bonds between the halves, but another tie, imperfect and possibly inadvertent, just occurred to me.
Mark Hammill was involved in some accident after the shooting of his first film in the saga, and this left him with some facial scarring that was apparently beyond an efficient solution by the makeup department of "The Empire Strikes Back". Instead of ignoring it or allowing the audience to assume that some random altercation had damaged Skywalker's demeanour, the script was modified to explicitly explain the changed face. That's the reason for that encounter in the beginning with the Abominable Snow Monster of the North.
Hayden Christensen was not visibly injured between the filming of his two "Star Wars" movies, but Anakin shows up in the latter with a distinct scar that gets no cinematic explanation. As Luke's could have been in a world without that beast battle on Hoth, this was the result of a battle outside of the movies. It just seems mildly odd to explicitly address one actor's slight disfigurement with an entire sequence in the story and then deliberately add one to the character's son without similar narrative focus.
And that's quite charming.
Best Scar? Jeremy Irons.