George Lucas being George Lucas
R2D2 served a lot of masters: Padme, Anakin, Bail Organa, Leia Organa, Luke Skywalker and even for a short time, Jabba the Hutt. In the expanded universe R2 helps the descendants of Luke Skywalker on their many adventures.
Carrie Fisher hanging with Warwick Davis
The robots are the main subject of Obi’s most famous quote “These aren’t the droids you’re looking for”. The line became a phrase used in any situation to indicate that the matter discussed is not at all relevant.