Talking about Star Wars: Episode II:

Ravenwood: One "mistake" I saw (not ruining anything) was that C3PO and R2D2 were around Beru and Owen Lars. C3PO was owned by Owen's dad, but amazingly in "A New Hope" [Star Wars: Episode IV] Owen had no idea who 3PO was and what he was capable of... I guess that is being nitpicky!

Skyhawk: Well it was 20 years later. Maybe he and beru smoked up a lot when they were dating and he forgot everything.