"Smoking does dreadful things to your lungs and is very bad for your heart." [R2-D2 beeps.] "Well, I know I don't have one, but Humans do, and I think we should set a good example."―C-3PO and R2-D2 via
Oh, I had nearly forgotten about this early eighties gem of a PSA where C-3PO busts R2-D2 for smoking!
screengrab via Hoth IcePlanet/YouTube