In the late 70s, when C-3PO and R2-D2 were taking a break from helping the Rebel Alliance fight off the Galactic Empire, they were assisting in bringing awareness to some of the issues that normal Earthlings face.
In this PSA from a galaxy far far away, R2 is sneakingly puffing away on a cigarette in the corner of the control room, when he is caught by 3PO. 3P0 scolds R2 saying smoking is very bad for the lungs and even though they don’t have them, they should set a good example for the humans.
http://www.youtube.com/watch?v=YWQgktBR6-w
See the two remaining PSAs after the jump.