Ha didnt know that stormtrooper one
In the original Star Wars, all the R2-D2 shots where he goes from 2 legs to 3 and moves, were all cut short. The outer legs were off center, so as R2 drove away, you can see the legs are pulling apart from his body.
(It was also a pneumatic system)
Also, you can always tell which R2 was the one Kenny Baker was inside. If you look closely at the feet, there are holes cut into the Battery Boxes for his legs to slide into.
