Okay, okay... This one is not very serious... but what fun it was to do!
The Douglas DC-2 transport was actually used by the U.S. Navy as the R2D-1. If a second version had existed, it would no doubt have been designated "R2D-2". Now considering that Douglas always used aircraft names starting with "Sky..." (Skytrain, Skytrooper, Skymaster, Skybus, Skyraider...) it was only too tempting to do an R2D-2 Skywalker!!!
For those of you out ther who don't know; the military has its own designations for aircraft. For example, the DC-3 above, is the C-47 Skytrain in the military. It was called Skytrain cause of all the cargo it could carry.