Alas it was at the EB Games Expo where I was manning Hasbro's booth (not to mention that my daughter was there), so I had to be on my best behaviour. I did tell him that I didn't want to hear spoilers, and that dropping spoilers without warning wasn't cool. But of course, the "damage" was already done. :(
But that's the point. Star Wars deliberately features those two droids as the only characters to appear in all the films. One of the main influences for Star Wars was Kurosawa Akira, a Japanese director famous for making samurai films. The Hidden Fortress inspired the story for A New Hope (the Death Stars and Starkiller Base are all hidden fortresses). Something that Kurosawa sometimes did was to tell the story not from the POV from a higher class nobility like a samurai etc., but from a lower class commoner such as a court jester, farmers, peasants etc. The lowest station that someone can have in the Star Wars universe is to be a droid, because they are basically a slave class. Episode VII tells much of the story through the eyes of the new droid, Beebee-Eight, but of course we do also see See Threepio and Artoo Detoo.
http://i6.photobucket.com/albums/y22...psbuq2vjro.jpg
So yeah, the consistency of the droids is very much intentional, as a story-telling motif that inspired by Kurosawa. The story in the Clone Wars episode Bounty Hunters was a retelling of Kurosawa's Seven Samurai, and the episode was made in his memory (as stated in the ending credits). Also, George Lucas initially wanted Mifune Toshiro to play Obi-Wan Kenobi, but Mifune declined, thus the role was given to Sir Alec Guinness. Other references to Kurosawa's samurai epics in Star Wars includes:
* The Force = a type of energy that flows through living things, inspired by the Japanese martial arts concept of "Ki(ai)" (though obviously greatly fantasised)
* Force Users are essentially space samurai. Just as romanticised image of the samurai is one of favouring swords over guns, Jedi and Sith prefer using light sabres over blasters, which both sides consider to be clumsy and uncivilised weapons.
* Some costumes are based on the Japanese Gi, notable Luke's farmboy clothes, Owen Lars' costume, as well as the standard apparel of the Jedi and Sith.
http://i6.photobucket.com/albums/y22...psnx2fjbgw.jpg
* Lexicon. The word "Jedi" is derived from the Japanese word Jidai (時代), which means 'period,' such as a historical period or period drama. Samurai stories are called "Jidai-geki" (時代劇), which means "period play." The word "Obi" (帯) is the Japanese word for 'belt, and "ken" (剣) means 'sword'. "Wan" (腕) can mean 'arm' (Tetsuwan Convoy = "Iron Arm Prime" ;)). The word "Sith," when rendered in Japanese phonology, sounds like the word for death (死す), thus a "Sith Lord," can be seen as a "death lord." On the Death Star. ;)
* The use of screen wipes, a signature technique from Kurosawa.
Star Wars does have a multitude of other influences as well, including Westerns and other science fiction. I'm not saying that Kurosawa's samurai epics were Lucas' sole inspiration for Star Wars, but they were among them, and to the point, this is why the droids are a recurring motif in the movies. :)