What I'd like to know is how C3PO and R2 could make multiple visits to Tattooine, yet, they don't remember it, nor, does Uncle Owen remember either one of them, in A New Hope.
C3P0 has his memory erased. R2 either seems to remember where Obi Wan lives, or is dumb enough to go trekking off into the desert to find him.
I think the martians got bored with watching the rover stuck and gave a helping hand.
I dunno... of course, I'd like to know why the unmasked Anakin/Vader looks like a 65 year-old man in Jedi, when he'd only be in his early 40's.
Or why Chewie doesn't seem to object Han's constant attacks on the Jedi and their religion when he so closely worked with them in the past.
What I'd like to know is why Duncan Idaho always had such wrotten luck.
I think they mention something about wiping 3PO's memory in ROTS. However, Obi-wan says he doesn't remember owning a droid like R2D2. Lucas didn't really care about continuity in the series, it was all about the cash. Don't be suprised to see the final trilogy, no matter how much he denies it.
Maybe Uncle Owen is a fleshist...all droides look alike
Owen never saw R2D2 long enough to remember him from any other astro droid...as for C3P0, he knew right away what kind of droid he was - but after 30 years or so and a different body he probably wouldn't know or care it was the same droid since there were a number of protocol droids with the identical shape of C3P0.
C3P0's memory is also said to be "erased" in Ep. III - a rather loose attempt to prevent a continuity error in him not remembering his home planet. But don't take movies too seriously - they aren't as fun if you do. :-)