This Poor Crippled Droid, on a quick inspection, looked very similar to an R2-series astromech droid but was in fact of an earlier model which was slightly larger, being 1.1 meters, rather than 1.0. It also did not seem to have the retractable legs of the R2's. The paint scheme on this particular droid was gray, much like the planet it inhabited. The wheel housings of this droid were missing from the bottom of the droid's "legs", and the droid (or perhaps someone else) had instead fixed small metal plates there instead so that the droid was still mobile, much like the runners on a sled. The droid moved along slowly, with a hobble which often caused people to feel sympathy for it.
When a group of Rebels landed on the planet Branth, where the droid had been all his life, he managed to find them. He communicated in much the same way as the later R2's, with series' of whistles and beeps. When the rebels landed, he was very lonely and so decided to follow the group wherever they went. It knew where the starbase (which had since been converted into the Prison Base) was located as it was long ago part of an experimental fighter program the Empire was performing before Branth was deserted.
When the group asked about his legs, he explained to them in a series of low chirps that he was damaged during a test flight, and the workmen had had to cut him out of the fighter. Because of the loss of its legs, it was deemed useless by the Imperial Navy and simply tossed out on the garbage to rust and die. The droid, refusing to accept this fate, attempted to repair itself the best it could and has felt shunned by Humans ever since.
The group of rebels agreed to take the droid along with them in their attempt to liberate the prisoners from the base, even though they knew that it would make any sort of sneak attack all but impossible due to how much noise the droid made simply moving about. Unfortunately, when in the base, the droid managed to get itself lost and so it simply went back to the group's ship. When it reached the ship, finding little else to do, it decided to "fix" the sublight maneuver drive, and took apart the magnetic drive coupler to do so. While in the middle of this, the rebel group arrived back at their ship to find him humming to himself and cleaning the parts. Because of this, the group had to take an additional 10 minutes to put the drive back together before they could take off.
What happened to the droid after this is unknown, though it was thought to have stayed with the group of rebels, becoming a member of the Rebel Alliance.