Anyone who has watched the Star Wars prequels in horror will appreciate Keith Martin's reinvisioned Star Wars backstory that attempts to explain how R2D2 and Chewbacca are the Rebellion's real top agents throughout the second trilogy.
If we accept all the Star Wars films as the same canon, then a lot that happens in the original films has to be reinterpreted in the light of the prequels. As we now know, the rebel Alliance was founded by Yoda, Obi-Wan Kenobi and Bail Organa. What can readily be deduced is that their first recruit, who soon became their top field agent, was R2-D2.
Consider: at the end of RotS, Bail Organan orders 3PO's memory wiped but not R2's. He wouldn't make the distinction casually. Both droids know that Yoda and Obi-Wan are alive and are plotting sedition with the Senator from Alderaan. They know that Amidala survived long enough to have twins and could easily deduce where they went. However, R2 must make an impassioned speech to the effect that he is far more use to them with his mind intact: he has observed Palpatine and Anakin at close quarters for many years, knows much that is useful and is one of the galaxy's top experts at hacking into other people's systems. Also he can lie through his teeth with a straight face. Organa, in immediate need of espionage resources, agrees.
It's interesting, especially given what a tough job it is to reconcile the trilogies.